Here is the claim and arguments by the modern Hindus:

https://www.speakingtree.in/blog/manusmriti-and-cast-system

 

1. Manu Smriti hails from an era when even the concept of birth-based caste system did not exist. Thus Manu Smriti nowhere supports a social system based on birth. Maharshi Manu took inspiration from Vedas (refer Rigveda 10.10.11-12, Yajurveda 31.10-11, Atharvaveda 19.6.5-6) and proposed a social system based on qualities, actions and nature of the individual.

 
2. This is called Varna System. Now the very word Varna derived from root word “Vrinja” means “Choice“. A similar usage happens in common used word “Varan” meaning “choosing” or “Var” meaning a husband chosen by the girl. This also shows that in Vedic system the girl had complete rights to choose her husband.

 

3. The biggest proof of Manu Smriti proposing Varna System and NOT Caste System is that in the first Chapter of Manu Smriti, there is mention of origin of 4 Varnas and no mention of castes or gotras. Had caste or gotra been important, Manu would have mentioned which castes belong to Brahmins, which to Kshatriyas, which to Vaishyas and which to Shudras.

 

4. In fact Manu Smriti 3.109 clearly states that one who eats by glorifying his Gotra or Family is considered an eater of his own vomit. Thus, as per the Manu Smriti that the self-proclaimed birth-based Brahmins or upper-castes believe in, the very act of glorifying their lineage or gotra to demand special privileges makes them deserving of condemnation.
 
5. Manu Smriti 2.136 states that one earns respect due to wealth, company, age, actions and knowledge in increasing order. There is no mention of family, gotra, caste, lineage and other non-factors to demand or earn respect.

Migration within Varnas
 
6. Manu Smriti 10.65 asserts that Brahmin can become Shudra and Shudra can become Brahmin. Similarly Kshtariyas and Vaishyas can also change their Varnas.
 
7. Manu Smriti 9.335: If a Shudra (uneducated) serves the educated ones, is polite, devoid of ego and stays in respectful company of knowledgeable ones, he/ she is considered as having a noble birth and stature.
 
8. There are several shlokas in Manusmriti that state that a person belonging to high Varna falls down to level of a Shudra (uneducated) if he does not conduct noble deeds. For example,
 
2.104: A person who does not worship the Supreme Lord twice daily should be considered a Shudra.

 

2.172. He who has not been initiated with teaching of the Vedas is a Sudra.
 
4.245: A Brahmin acquires brilliance through company of noble persons and avoiding bad company. On contrary, if he indulges in bad company, he becomes a Shudra.
 
Thus clearly, Brahmin refers to a scholarly person who conducts noble deeds. And Shudra refers to an uneducated person. This has nothing to do with birth in any manner.

Our Comments:

Let us look at your first proof that there is no Caste System By Birth in Manusmriti:

 Modern Hindu said:

 5. Manu Smriti 2.136 states that one earns respect due to wealth, company, age, actions and knowledge in increasing order. There is no mention of family, gotra, caste, lineage and other non-factors to demand or earn respect.

 

Don't you think that it is out of context conclusion? Let us read this verse along with the next verse. 

Manusmriti, Verse 2.136 + Verse 2.137

Wealth, Relation, Age, Action and Learning, as the fifth,—these are the grounds of respect; (among them) that which follows is weightier (than that which goes before it).—(136) Among the three (higher) castes, he, in whom there are present most of these five, and of high degree, deserves (greater) respect; as also the Śūdra who has reached the tenth stage (of life).—(137)

 But do you know what does this 10th stage of life of Sudra means?Let us see the commentary of verse 2.137:

Medhātithi’s commentary (manubhāṣya):

... The ‘tenth’ stands for the last stage of life, and indicates extreme old age. Thus then, in case of the Śūdra, ‘wealth’ and ‘relations’ do not constitute grounds of respect, in relation to tho three higher castes. This is clear from the fact, that the Text specifies the ‘tenth stage.’ ‘Action’ and ‘Learning’ are not possible in the Śūdra; for the simple reason that he is not entitled to these.

Would you please mind and tell us:

* Question 1: Why Sudras not allowed to LEARN the sacred texts and do the Action? 

* Question 2: Don't you think without Learning, a Sudra will again turn to Sudra while according to your own conclusion an uneducated person is a Sudra. 
 

It is difficult to consider that creature to be Divine who wants to keep a person uneducated, while he was born in a lower caste. 

  Modern Hindu said:

Migration within Varnas
 
6. Manu Smriti 10.65 asserts that Brahmin can become Shudra and Shudra can become Brahmin. Similarly Kshtariyas and Vaishyas can also change their Varnas.

Don't you think once again there is some deception and distortion here and things are put against the context?

Let us make things clear here first by reading this Verse 10.65 along with the preceding verse 10.64 in order to see the proper context:

Manusmriti, Verse 10.64 + Verse 10.65

If the child born from a Śūdra woman to a Brāhmaṇa goes on being wedded to a superior person,—the inferior attains the superior caste, within the seventh generation.—(64) The Śūdra attains the position of the Brāhmaṇa and the Brāhmaṇa sinks to the position of the Śūdra; the same should be understood to be the case with the offspring of the Kṣatriya or of the vaiśya.—(65)

Medhātithi’s commentary (manubhāṣya):

—‘A maiden born from a Śūdrawoman to a Brāhmaṇa father,—if she is ‘wedded to’—acquires the capacity for bearing children, by becoming conjoined in wedlock to—a person of a superior caste i.e., the Brāhmaṇa,—and the girl born of this maiden is again married to a Brāhmaṇa,—and this goes on for seven generations, then in the seventh generation, the child that is born becomes a regular Brāhmaṇa.’

Therefore change of the Varna is happening here only through (1) Marriage in higher caste and (2) then again marriage in the higher caste for 7 consequent generations. 

Is it not totally against your claim that there is no Caste System by Birth in Hindu Sacred Texts?

 

  Modern Hindu said:

 
7. Manu Smriti 9.335: If a Shudra (uneducated) serves the educated ones, is polite, devoid of ego and stays in respectful company of knowledgeable ones, he/ she is considered as having a noble birth and stature.
 

Here the change of Varna is taking place through "servitude" of Brahmans, but it has nothing to do with the learning, which was banned upon them as Sudras. 

Actual translation is: 

Manusmriti, Verse 9:335: If he is pure, attendant upon his superiors, of gentle speech, free from pride, and always dependent upon the Brāhmaṇa,—he attains a higher caste.—(335)

 

  Modern Hindu said:


8. There are several shlokas in Manusmriti that state that a person belonging to high Varna falls down to level of a Shudra (uneducated) if he does not conduct noble deeds. For example,
 
2.104: A person who does not worship the Supreme Lord twice daily should be considered a Shudra.

4.245: A Brahmin acquires brilliance through company of noble persons and avoiding bad company. On contrary, if he indulges in bad company, he becomes a Shudra.
 
Thus clearly, Brahmin refers to a scholarly person who conducts noble deeds. And Shudra refers to an uneducated person. This has nothing to do with birth in any manner.

 

We are afraid that you presented only one side of the Manusmriti, while hid the other side, which is as under (link):

 

1. For the welfare of humanity the supreme creator Brahma, gave birth to the Brahmins from his mouth, the Kshatriyas from his shoulders, the Vaishyas from his thighs and Shudras from his feet. (Manu’s code I-31,)


2. God said the duty of a Shudra is to serve the upper varnas faithfully with devotion and without grumbling. (Manu 1-91) Manu is not satisfied with this. He wants this servile status of the Shudras to be expressed in the names and surnames of persons belonging to that community. Manu says:


3. Let the first part of a Brahman’s name denote something auspicious, a Kshatriya’s be connected with power, and a Vaishyas with wealth but a Shudra’s express something contemptible. (Manu II.31)


4. The second part of a Brahmin’s name shall be a word implying happiness, of a Kshatriya’s (a word) implying protection, of a Vaishya’s a term expressive of thriving and of a Shudra’s an expression denoting service. (Manu II. 32.)


5. A hundred year old Kshatriya must treat a ten year old Brahmin boy as his father. (Manu 11-135)


6. The Brahmin should never invite persons of other varnas for food. In case, the latter begs the Brahmin for food, the Brahmin may give them some left-over. Even these left-over must be served not by the Brahmin but by his servants outside the house. (Manu II2).


7. He who instructs Shudra pupils and he whose teacher is a Shudra shall become disqualified for being invited to a shradha. (Manu III. 156.)


8. A Shudra is unfit of receive education. The upper varnas should not impart education or give advice to a Shudra.It is not necessary that the Shudra should know the laws and codes and hence need not be taught. Violators will go to as amrita hell. (Manu IV-78 to 81)


9. “Let him not dwell in a country where the rulers are Shudras.” (Manu IV. 61)


10. He must never read the Vedas in the presence of the Shudras. (Manu IV. 99.)


11. Any country, where there are no Brahmins, of where they are not happy will get devastated and destroyed. (Manu VIII-20 to 22)


12. A Brahmana who is only a Brahman by decent i.e., one who has neither studied nor performed any other act required by the Vedas may, at the king’s pleasure, interpret the law to him i.e., act as the judge, but never a Shudra (however learned he may be). (Manu VIII.20.)


13. The Kingdom of that monarch, who looks on while a Shudra settles the law, will sink low like a cow in the morass. (Manu VIII. 21.)


14. Any Brahmin, who enslaves or tries to enslave a Brahmin, is liable for a penalty of no less than 600 PANAS. A Brahmin can order a Shudra to serve him without any remuneration because the Shudra is created by Brahma to serve the Brahmins. Even if a Brahmin frees a Shudra from slavery the Shudra continue to be a slave as he is created for slavery. Nobody has the right to free him. (Manu VIII-50,56 and 59)


15. A Shudra who insults a twice born man with gross invectives shall have his tongue cut out; for he is of low origin. (Manu VIII. 270.)


16. If he mentions the names and castes of the (twice born) with contumely, an iron nail, ten fingers long, shall be thrust red hot into his mouth. (Manu VIII. 271.)


17. If a Shudra arrogantly presumes to preach religion to Brahmins, the king shall have poured burning oil in his mouth and ears. Manu VIII. 272.)


18. A Shudra who has an intercourse with a woman of the higher caste guarded or unguarded shall be punished in the following manner; if she was unguarded, he loses the offending part; if she was guarded then he should be put to death and his property confiscated.” (Manu VIII. 374.)


19. A Brahman may compel a Shudra, whether bought or unbought, to do servile work for he is created by the creator to be the slave of a Brahmana. (Manu VIII. 413.)


20. No Shudra should have property of his own, He should have nothing of his own. The existence of a wealthy Shudra is bad for the Brahmins. A Brahman may take possession of the goods of a Shudra. (ManuVIII-417 & X129)


21. A Brahman may seize without hesitation, if he be in distress for his subsistence, the goods of his Shudra. The Shudra can have only one occupation. This is one of the inexorable laws of Manu. says Manu. (Manu VIII. 417)


22. A Shudra who wants to just fill his stomach may serve a Vaishya. If he wants a permanent means of living he can serve a Kshatriya. But if he wants to go to heaven or wants higher or superior birth in the next generation he must serve a Brahmin. (ManuIX334 & 335)


23. The most sacred duty of a Shudra is to serve the Brahmins, always, reciting the words “Brahman” with utmost devotion. Such a Shudra will get salvation. Otherwise he will die a worst death and will go to the worst hell. (Manu X-121)


24. But let a (Shudra) serve Brahmans, either for the sake of heaven, or with a view to both (this life and the next) for he who is called the servant of a Brahman thereby gains all his ends. (Manu X. 122.)


25. The service of Brahmans alone is declared (to be) an excellent occupation for a Shudra for whatever else besides this he may perform will bear him no fruit. (Manu X. 123.)


26. They must allot to him out of their own family (property) a suitable maintenance, after considering his ability, his industry, and the number of those whom he is bound to support. (Manu X. 124.)

 

All these hated teachings, all these contradiction, all these insane punishments of Sudras ... all this is implying only one thing i.e. the "human nature". This has nothing to do with teachings of any divine creature. 

Every religion put a lot of stress upon "knowledge/(useless knowledge) of the religion" and "worship" of the creator. 

There are about 100 Verses in Quran which are talking about the "ILM" i.e. knowledge. But all this knowledge is practically useless are it has mostly to do with the religion and there are less of the morals, and then sharia laws which are against the humanity.