Of course the Nazis weren’t right by our standards, and of course they were/are by their own. But by what universal standard can we judge their morality against ours? How can we know that what we think is right is the objective morality?

Saying “it just is” really just means “I think so”, and it there’s as much reasonable backing for you to say it “just is” wrong to be a nazi as it is for someone to say it “just is” wrong to be gay.