The claim itself isn't a sacred cow, it's that the claim challenges the inferred sacred cow that: "of course the gender pay gap is mostly because of sexism".
I can drop the "sacred cow" phrase (it might be politically incorrect after all
), instead what if I called it "an article of faith" (oops, that might be PI as well!).
So I think this is an example of a common situation. Certain ideas become articles of faith, and to challenge those ideas is viewed as evil. Those challenges might be called "racist" or "sexist" or "insensitive" or "offensive" and so on. So perhaps we can say that when such feedback is offered, it's a sign that PC boundaries have been trampled on.
I guess I should understand how you're using the word "antagonistic"? If you're thinking it's antagonistic for the sake of being antagonistic, then I disagree. If you're saying it's antagonistic because the nature of criticism is antagonistic, well... sure.