I think that's a cultural thing, not a racial thing and it just happens that some black women come from a culture in which it is acceptable for women to be very forceful and domineering. This might make them less attractive to your average white joe but not all black women are like that. I know a couple of very sweet, meek black girls.
I myself am forceful, domineering and don't suffer foolish men gladly. Then again I come from Kenyan culture and have four aunts who have children with absent fathers and they can't seem to do anything about it. Thus, I don't find what I've seen of the black male persona attractive.
But what you have to remember is that everyone is an individual, we all have our quirks, our good points and our bad. And you never know whom you might be attracted to.