Battlestar Galactica's Ron Moore does a lot of Q&A in his posts to the official blog for the series. In his latest post, Moore talks about gays, or the lack thereof, in the series...

[Question:] ...so far that there are no gay characters on Battlestar Galactica. I'm just wondering if it's the case that homosexuality doesn't exist in the world of Battlestar, or it does exist, there are gay characters, and it just hasn't been discussed because it isn't relevant toward the plot[?] ...

[Answer:] ... I think homosexuality definitely exists in the world of Galactica, ... It's something that gets talked about internally periodically, but so far there hasn't been a good story or character arc or scene that's seemed like a good way to establish the fact without really hanging a big neon sign out that says, "See, we're doing a gay theme now!" ...

My first reaction was, jokingly, Galactica has primarily focussed on the military, maybe the 12 Colonies have their own "don't ask, don't tell" policy? I've never expected to see gay characters in Galactica, we've seen little enough of the civilian population without going even deeper into a minority group. Unless perhaps one of the surviving ships in the fleet was the 12 Colonies version of an Atlantis Cruise.

I'm a bit surprised the writing team has considered it more than once.

I think a problem for any show trying to introduce a gay theme or character is that it's hard to do with just one character. For homosexuality to be relevant to the story, you would really need a love interest. Galactica's love triangles and relationships are so complicated already, plus the sci-fi element, even a well done gay plotline would probably be too much for most people to follow.