You know, even as jaded as I am, there's something about the girl-on-girl thing that just gets me where I live. Which puts me, I think, pretty solidly in the majority; I don't think you can ask for a more typical "guy thing" than that.
Yeah, I know, I hate to be cheesy and cliched, and I am at least a reasonably enlightened guy, but, I mean, damn!
So what is it about the "hot lesbian action" thing, anyway? It's a cliche that guys are into this sort of thing because...well, we are into this sort of thing. It's depressing, really; there's nothing rational about it. It just grabs us by the back part of the brain--the part that knows nothing of reason--and says "Hey! Hot girl on girl action! Gimmee some of that!"
I had a cognitive science professor back in my college days who swore it was biological. Said it crosses all cultural and educational lines, and theorized about how humans are the only primate whose females don't have an obvious outward sign that they're sexually receptive, but that guy-on-girl action is more likely to raise a territorial/competitive reaction, whereas girl-on-girl behavior is clear and unambiguous evidence that the females are sexually receptive and there's no male there to represent a challenge...
I dunno. I think that's a difficult theory to support.
But still. Damn!