Why did people hate black people?

People still do. They hate darker skinned people because they hate people so different. That's jsut the way hw is it. People hate differences, especially beneficial differences. When blacks were brought over to the U.S they were very strong, could work for long hours, were immune to most of the sicknesses prevalent in Europe and were therefore hated. They were also seen as "less human" by some, but it may simply be that some thought they were a threat.