If there's an overall shortage, then the black Democrats must have lots of white staffers. Not that there's anything wrong with that.
In general, I'm not a believer in "lack of proportional representation" being an indicator of some kind of racist conspiracy, but I do think that here it does indicate something. We all have a tendency to hire people we know, people who aren't an unknown risk. Who travel in the circles we do. I a predominantly black city like DC, you'd thing the "proportional representation" would lead to more minorities. How did the sensitive Democrats become so insensitive?
Chalk it up to more weird DC, where the laws that pass for us, don't apply to them, because they write themselves out of it.