Holocaust, war, and human life

During the Holocaust about six million people died. They were murdered because of their race, sexual orientation, and mental or physical disabilities. The Nazi's did not like these people because they were different. In war we fight because of our differences, we dislike people because of their religion. In human life everyday people are tortured and murdered because of their race, religion, sexual orientation, physical appearance, and just because they are different. Why are these people constantly shamed because they are different? What makes people think that just because they don't believe in the same stuff as someone else that it is okay to kill them? There are little Hitlers all over the world, running around tormenting people who are different all the time but no one knows why.