Why are somebody's skin color and Ideological beliefs considered good enough reasons to hate them?

Why do people hate others just because of their skin color, race, difference of opinions or beliefs ? Why are players of African or Asian descent ridiculed in football games and religious people ridiculed in today%26#039;s comedy television shows?|||My theory: people hate what they cant understand.|||I think hate derives from a lack of knowledge or understanding so as long as someone dresses, looks, or acts different than another person hate will always be around. Hate is also a scapegoat for other people to hide their insecurities