Yeah, people usually only talk about people getting into jobs and positions that are highly sought after, so everyone wants to see more women in science and everyone thought it was fantastic that a black man became US president but no one seems to say "hey, there should be more female garbage men."

They're making a barely distinguishable but critical mistake. The point is not that certain groups do get into certain places in society; the point is that the roadblocks preventing them from gaining access are removed. (This is sort of tied in to what humanodon said about balance.) Focusing on getting certain people into certain places is part of the illusion of the whole "glass ceiling" thing. It isn't about numbers. Attitudes toward black people, overall, are probably not going to change significantly just because Barack Obama was elected.

Although, in the long term, it probably does make a difference. And it does suggest that at least people are willing to elect a black president, but then that makes it a symptom of changing attitudes, and not a terrifically powerful causal factor. (And, of course, the fact that many would have voted for him because he was black is itself a problem.)