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Perhaps not, but it might be a significant component of it.

Think about it from the point of view of someone who doesn't interact with black people very often: they probably can't tell whether a person is a gangbanger or dangerous or not. If you can't distinguish a potentially dangerous black individual, then everyone black person becomes suspect, especially if you have a negative view of the group to begin with. People's natural risk aversion and fear of unfamiliarity just heightens this affect.

But presumably, that same person is more familiar with white people and can distinguish real threats, from, say, their neighbor or the kid down the block.