I believe the psychological condition you are referring to is confirmation bias.
There will always be some degree of confirmation bias involved in everyone's interpretation of a given set of evidence, but in this case I think the overriding factor is racially motivated prejudice. Brown is black and therefor more likely guilty than a white.
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Since I am not white nor black and I have no special love for blacks, my opinion is far less likely to be clouded by that factor. I dont hate them, but I dont hang around with them either. You wont find too many Indians who do.

It IS true that I have had personal negative experiences with meth addicted people and hat meth can do to a person and to a community, but even Jesus pointed out evil when he sa it.