It is possible for something to be important to talk about,
and for the way it's talked about to be stupid. In fact, I think it's quite common. I agree with paganel that a lot of US race discourse is stupid. I agree with you that sometimes it's important to talk about race. There's no contradiction between those.
(But I don't think "white supremacy" is a good way to think about the Nazis' hatred of Jewish people. They were white supremacists, but they hated the Jews for other reasons and if by some miracle they had abruptly stopped being white supremacists I think they would have gone right on persecuting Jewish people.)