Racism

I've been kicking around and chewing on some ideas about the causes of racism. Projection of one's own hatred of and ill-will towards The Others? "I hate and want to hurt The Other because of the color of his skin, making it reasonable to assume The Other feels the same way."
Guilt or Distotion and fear of having the status quo upset? "My Kind have unfairly held the upper hand for so long that it is reasonable to assume The Others would (justifiably?) take it away at any price."
Plain old selfishness, ignorance and lack of exposure?

Why do we do it and How do we stop it?