If we, as humans, didn't judge other people based on color, there would just be something else in it's place. It's human nature to create classes, unfortunately. But if it wasn't racism, it would just be another aspect of the physical body.
People are stubborn and can't let go of tradition or ignorance. They must justify previous mistakes by validating them today. Some people refuse to grow- perpetually stuck in the past with ancient ways of looking at the world when we are light years ahead of them in the thinking department. Our enlightened perspectives are too much for their feeble intellect to grasp. Call it evolutionary divergence because I'm sure at a biological level even, they are relatively stupid.
One race thinks they are superior to another one. Most likely raised that way. Some go so far as to hate persons that are not of the same race. I dont agree. If you cut someone the blood is the same color in all races. God created all men equal & loves everyone.
I am only two generations away from the worlds most despicable slavery trade. So many was to degrade a human it will never ever be able to be changed. Racism, ageism, sexism, and many other ways to feel bullied or left out will always have to be a part of human life.
Because we have not learnt to set aside our differences and grow in unity. Secondly,I believe that it has lot to do with our leaders.They influence us since every country is seeking "status"in some kind of way...sad...good question by the way.
The answer is simple --sin. We harbor evil thoughts about other people and commit evil acts against other people because of sin (Romans 3:10-23). Sin appears to make us innately suspicious of people who look differently from us. Only through the transformative power of salvation in Jesus Christ can racism be overcome (2 Corinthians 5:17). Only through seeing all other people as being created in the image of God (Genesis 1:26) can we rid ourselves of racial prejudices. http://www.blogos.org/gotquestions/racism.html