You can certainly say, Jews believe x, citing some tenet of Judaism, or Catholics believe y.

(You can actually *say* whatever you like, as I’m nearly a free-speech absolutist).

But you *should not* say, “White people are evil, or Jews are vindictive” because that is wrong. It is wrong in both senses of the word — incorrect factually and also unethical to smear an entire group with pejoratives based on the actions of a few people in the group.

Now if you were to say the KKK is racist, that would be okay because racism is a tenet of their belief system! If you’re not racist you wouldn’t be in the KKK (as far as I know.)

But just smearing people with generalizations based on the actions of a few people in their group is wrong.