The Holocaust

I feel that the holocaust is one of the worst events that took place ever in history. I don't understand how a whole group of people can treat another group like that just because of their religion. Also, I don't get why whole countries of people backed the terrible crimes being committed by the Nazi's. If I lived somewhere and knew that was going on, I would try to at least do something to stop it. Many people probably didn't agree with it, but did nothing about it. That's why six million people died in the holocaust. How can somebody think that others aren't as good as them just because they don't have the same religion or hair and eye color? That would take a truly evil person, that was messed up in the head. On the other hand, why didn't the US get involved in the war sooner when we knew the terrible things going on? Our isolationist policy seems selfish. The holocaust was a terrible thing.