here is a simple paper that was one of the first links i clicked on. Otherwise, you can find endless studies on unconscious bias.
The point is simple, you can claim all day long and genuinely believe that you are not biased, not prejudiced, not racist etc etc etc. The difference in those who do and don't is that those who do are usually better and spewing a socially acceptable answer. The problem in all of this is that unconscious mental processes drive conscious thoughts. You don't know what drives your conscious thoughts. You just know what you say and what final ideas rose to conscious awareness. You most often don't know why you think or feel a certain way about something, though you desperately want to believe you do.
Testing however, reveals that our brains are very dark and disturbing places.
http://diversity.arizona.edu/sites/d...._a_primer.pdf
To believe that people are rioting in Ferguson because they have legitimate concerns about race in america is pure fantasy.