It's probably due to foreign policy and domestic civil liberties issues. Most of the people I know on the left who aren't voting for Obummer are doing so because of the adminstration's love of Droney the Flying Kiddie Killer and continued domestic civil liberties rollbacks in the name of the WOT.
I realize that might be part of it, but if you saw this guy you'd still be surprised since, as I said, LGBT activism and stuff like this is by far one of his biggest issues he cares about.
I dunno, if that was my primary concern I'd be scared as fuck of having Romney put in instead of the guy who's pushed those issues forward more than any other president in history. And I'd want to reward the guy that pushed those issues forward with my vote. I mean, Biden just said the other day that transgender discrimination is the civil rights issue of our time. Hell, just saying that he should get a vote from someone like this guy, since there's no way in fuck Romney or Ryan would say anything remotely like that.