The Holocaust is nice and convenient to teach in American schools because it points fingers at someone else!
If in the obligatory anti-racism curricula we were discussing slavery then you would always get the, "well, my ancestors fought for the South and they did not own slaves." Nevermind that much of the lynching was not done in the South either. But with the Holocaust it can be everything and nothing. Nazi mad scientists or brown-shirted bullies. Dictators and demons. Witches and warlocks. Accordingly, the Germans were not Nazis either.
Oh, and why is it so important to teach against racism in school? Well, for the same reason that it is important to promote free trade; it reduces a cultural barrier to the global expansion of financial markets and the exploitation of cheap labor.
