http://science.sciencemag.org/content/336/6083/825.full

Roots of Racism

why people usually discriminate people by the skin? because from the skin we knew that where they are come from. and usually people can see from their faith when they know what their faith they would choose people who same faith with them and distinguish another faith. and the last by ethnic people usually see, when they do not like some ethnic then they would not like the people from that ethnic.
Racial prejudice apparently stems from deep evolutionary roots and a universal tendency to form coalitions and favor our own side. And yet what makes a "group" is mercurial: In experiments, people easily form coalitions based on meaningless traits or preferences—and then favor others in their "group."

as human we should not distinguish people by ethnic, faith or race. because we are same. we are from God. God create us same as another so do not see people from therace, faith and race. do not judge the book bye the cover.