bi girl here, hope you don’t mind me chiming in. =)
I think I’m kinda weird on this subject. the concept of guy-guy sex doesn’t bother me, nor does gay romance (any more than cutesy bullshit between any couple I’m not involved in). I read & thoroughly enjoy a few mangas with male homoeroticism as a focal point; I’ve watched a few episodes of Queer as Folk and actually been quite turned on by the sex scenes and flirting and steaminess between guys there… but I caught a few minutes of an HBO special on porn, saw two guys fucking in earnest, and almost literally vomited. and seeing a man with another man’s penis in his mouth makes me cringe and shudder like I’m in a tub of roaches, way worse than the actual fucking. these were hot guys, too.
helpless look I don’t understand it. if I had to venture a guess, it might have something to do with my aversion (but not repulsion, by any means) to anal sex (I fast-forward through those scenes in straight porn). and yet for some reason two guys fucking missionary style, though I’ve not actually seen it, I don’t see bothering me nearly as much.
but as to the OP (since that had nothing to do with it…), I’d guess 4. but I’m definitely not a gay guy, so I’m pretty unqualified to answer that.
as to the phenomenon of some gay men being squicked by het sex and/or cunnilingus, I would guess that it’s often really just a repulsion by the vagina in general. I understand it; I used to be that way and probably still would be if I hadn’t met an amazing girl who just radiates sexual energy and brilliance, such that there was no possible way for me to be grossed out by anything about her, which has evolved into an appreciation of females and their anatomy in general. shrugs weird world.
anyway, I think it’d probably go the same way for lesbians revolted at the thought of het and/or guy-guy sex (aversion to penis).
and as a complete aside:
which is about all it takes to get a straight guy off, and that’s why you see it in porn for guys, not actual lesbian porn. with the exception of some of Jenna Jameson’s older (for-straight-guys) stuff; she always got way into it (and now, shock of the world, she thinks she might be a lesbian laughs)…
and yeah, as someone who potentially would find lesbian sex appealing, I am rather turned off by most of the stuff that goes on in made-for-guys “lesbian” sex scenes. it’s a double-edged sword, though, because ACTUAL lesbian porn tends to have one or a combination of a) butch girls, b) girls that aren’t as hot, and/or c) strap-ons (SHUDDER). sigh guys’ porn it is, then.