The Nazis themselves are horrible, racist people, but that doesn't mean the person telling the joke about them has to be racist. In fact, that doesn't even make sense - especially if it's an anti-Nazi joke. Of course it's mean and cruel to make fun of the people who died in the Holocaust, but the thing is, what if the joke just makes fun of Nazis? How is that racist!? Oh, so now it's racist to be anti-Nazi?