There's no rational explanation for racism. No matter how selfcentered you are you still have a selfinterest in fostering cooperation. No matter how superior you think you are, no matter how much despise another person, it's just not rational to stop cooperating.

In all honesty, between arrogance and stupidity, I believe stupidity is the biggest factor on here. Not all racists are arrogant, though being racist kinda makes them arrogant cause they believe they are the superior race. I feel it is within human nature to react to what is different negatively at times, and as bad as that may be, that is probably the biggest factor. Albert Einstein once said that "Common sense is the collection of prejudices by age eighteen" when we are little and we touch something hot, we gain the prejudice that "hot things are painful" I hypothesize prejudice in the context as a social issue (e.g. racism, homophobia, sexism, etc) a lot of the time may have been acquired at a young age for some particular reason. I have come across racists whom stop being racist in adulthood, but haven't come across many racists whom become racist in adulthood, of course that could just be flawed by my own personal experience. I think it is more rather immaturity that causes racism than anything else, on a societal level and individual level. I have never been racist but I used to hang around a bunch of hardcore racists.

I think it's a crying shame that racism exisats still to this day.