A friend pointed out the other day that liberals love to mock people who, if accused of racism or some other "ism," defensively say, "Some of my best friends are black/gay/whatever...." But in fact that is actually a perfectly good illustration of one's open-mindedness. If one hates blacks, or gays, or any other group, and judges them as wanting because of that identity, one would not befriend them. This seems fairly self-evident; my friend is right.
But for liberals, of course, actual open-mindedness isn't enough. Liberals demand the close-mindedness inherent in reciting the liberal shibboleths of the day, including that there are no racial or gender differences. Should one notice a fact to the contrary, and be naive enough to actually blurt it out, subsequently claiming friends of other groups as proof of goodwill is to be sneered at.
As usual, the liberal definition of open-mindedness means the opposite.
One phenomenon I've noticed is that liberals are much more likely to become friends with someone because he's black or gay. It's a great way for a liberal to prove to himself -- and the world -- how hip and open-minded he is. Such liberals often tend to "show off" these trophy friends.
Personally, if I were black, I'd prefer a friend who liked me for myself, not for my potential as a prop.