Yeah we sort of established that the government is stupid and wrong and that homosexuality isn't a disease. But nice find. You should see if GLAAD knows about it.
rabbit, no, we haven't. We haven't established whether it's genetic (nature vs. nurture), and if it's not genetic, whether it's nurture vs. choice.
We haven't established these things because there have not been controlled, conclusive studies about them. Show me the university study where they tried to raise someone gay, or they cross-bred gays and lesbians for several generations to see if they became gay.
Find me a single gay person who says he chose to be gay.
The problem with this is that is that you cannot rely on honest self-report, particlarly about something so stigmatized.
Better yet, watch a movie of two guys screwing each other, and try to masturbate to it. How can you say that some normal person (like you) could CHOOSE to find that appealing?
Perhaps the genetics vs. nurture is unsolved, but I'm convinced beyond any doubt that a guy can't choose to get hard by looking at a guy's ass.
Take a look at, for example, Craigslist personal ads under the section "man for man" or "casual encounters" of any big city. A lot of the titles, even, say that guys are looking to take care of a straight man (giving him a BJ) - particularly married ones, probably looking to avoid STDs. I generally find this repulsive, correct. But I imagine the sex-deprived-enough man (Newby, for example) might just give in one day to get head (rumors suggest this might have already happened. Yes, I like to pick on him when he's out of town and can't read this). He doesn't really care for it, but hey, they guy said he'd put on some straight porn and he could just relax.
Now, the blowee (receiver) has just had a very powerful pleasure response associated with the oral-sexual stimulus provided by another man. So the next time he's looking to get head, he might be a lot less opposed to it. Eventually, this may become conditioned for a person to find it pleasurable, or to associate gay sexual acts with sexual pleasure, thereby yes - having become gay (or bi) by choice.