I think I get his point, which seems to be that birth-language organizes thought and, therefore, the worldview it creates (such as a caste system imbedded in language ) is more difficult to alter (perhaps impossible without altering the language) than beliefs not hardened into language.

(Thought experiment: What if English did not have gendered pronouns?)

However, to take this point, extrapolate it and make pronouncements about the validity of the experiences of cultures not his own seems, to me, hubristic.