For African-Americans, it's the subtle kind that drives them crazy:
As reported in the September issue of Psychological Science, black volunteers who had witnessed unfair but ambiguous hiring decisions did much less well on the Stroop test, suggesting that they were using all their mental resources to make sense of the unfairness. Interestingly, white volunteers were more impaired by overt racism than by the more ambiguous discrimination.
Salvatore and Shelton figure this is because whites rarely experience any racism; they do not even notice the subtle forms of racism, and are thrown off balance when they are hit over the head by overt acts. Many blacks, by contrast, have developed coping strategies for the most hateful kinds of racism; it’s the constant, vague, just-below-the-surface acts of racism that impair performance, day in and day out.
That makes sense to me. I have no problem with overt, blatant homophobia. I can laugh at it. It's the kind you can feel but not see explicitly that gets under your skin.