Oh, I agree with you. Just showing that there is an exception.
Eminem's being white plays a huge part, definitely, but it isn't as simple as that. Because of his crossover appeal—I'm sure we all know (white) people where the only rap they listen to is Eminem—his misogynism, homophobia, etc. is that much more of a "threat." Therefore, he is the target; for all the millions rap albums sell, it's still largely perceived as a black thing, which isn't the suburbs, which, in turn, isn't worth acknowledging by your average special interest group.