“I don’t know or care what “bigotry” or “sexist” means, but if someone were to say or even imply that any halachos or mesorah or minhagim are wrong or bad or mistaken or ought to be modified, they are violating numerous issurim.”
Once again, you need to separate out minhagim. There exists such a thing as a “minhag shtus” or a minhag that once had a proper basis but no longer. Even in halacha things can be modified if the circumstances change or the accepted psak changes.
Saying a minhag is wrong is not assur. Even saying that a common psak is wrong is not assur, so long as your are making a halachic argument.