I don't think he is. He seems like the type that would be open about it and use it as yet another reasons to wildly foam at the mouth on social injustice. I think he's just another example of more and more straight men like Jon Stewart that are becoming strongly supportive of gay issues. We're even seeing straight former admirals and generals speaking out against DADT. This seems to be indicative of a slow but steady paradigm shift in much of the straight male population to our favor.
I've heard rumours in the past that he was. (Keith Olberman) But I don't think he is. As someone here already said...if he was Gay, he would have no problem being out. Too bad he is not. Would be a bloody fantastic spokesperson. Cheers, Keith