Not even the only AA male. There are at least two others than I can think of, though neither is as well-known as Williams. (One of them is also a commentator: Aaron Freeman.) There are also some others who have worked there in the past but no longer do, most notably Tavis Smiley and Tony Cox. I'm not sure where Cox is at the moment, but Smiley now works for PRI, and his show is widely carried on NPR stations, including mine. I listen to it all the time.
Honestly, I can't really tell if it is NPR or Williams that is persisting in making a public situation out of this, but it shouldn't be. It's a personnel matter, and as such it should be dealt with in private. If Williams wants to sue, then fine, he should file suit, but trying this in the court of public opinion is bizarre. (It smells to me like someone somewhere has a profit motive in all this hoopla, but right now the various accusations and justifications are flying so thick and fast that I can't figure out exactly where that motive lies. However, it wouldn't surprise me if the agitator turned out to be neither NPR mgmt nor Williams, but some third party.)