I get that they are quoting scriptures, but still, there is no context in that page for anybody who reaches it using google that this is not actual advice. There are things like this:
Those sons of the twice-born, begotten on wives of the next lower castes, who have been enumerated in due order, they call by the name Anantaras (belonging to the next lower caste), on account of the blemish (inherent) in their mothers.
From a Kshatriya and the daughter of a Sudra springs a being, called Ugra, resembling both a Kshatriya and a Sudra, ferocious in his manners, and delighting in cruelty
The son that is begotten by a Brahmana upon a Sudra wife is called Parasara, implying one born of a corpse, for the Sudra woman's body is as inauspicious as a corpse.
His third wife being of the Sudra order is regarded as very inferior.
A son that takes birth under circumstances other than those mentioned above, comes to be looked upon as a very inferior one If a person of a lower order begets a son upon a woman of a superior order, such a son is regarded as outside the pale of the four pure orders. Indeed, such a son becomes on object of censure with the four principal orders.
I'm perfectly fine with scholarly discussion of religious texts, but it should be clear when they are scholarly discussions by the stack schange community, tags or content of the questions and answers.
Usually, religious StackExchange communities are not limited to scholarly discussion. Questions and answers about actual advice in those communities should conform to the same norms as the rest of the StackExchange communities.