I agree everything in life is primarily a choice, and I believe so even if you're being beaten or have a gun to your head. When it comes to ways of thinking or states of mind, if people can for example recover from major problems such as depression, I have no doubt they can also decide to stop believing and start questioning all the stuff they were taught from their childhood, providing they feel something's wrong or just don't feel comfortable.
That said, choosing your sexual condition is not the same as choosing not to marry. I mean, I couldn't get to feel attracted to a woman, in the same way as I suppose a lesbian couldn't feel attracted to any man. If you state that homosexuals (the real ones, not the pretending ones) could choose to become heterosexuals, then the opposite would also be true, which is clearly not (at least not in my case).
Of course, one can choose to become a celibate... but this should be a personal choice, not an imposition based on your sexual orientation. I mean, some people think sex for the sake of sex is immoral, but do they apply their morals to straight people or just to gays?
Anyway, despite gays' protests can be quite noisy and tiring, I don't find them more annoying than any other kind of protest (at least gays' are usually peaceful), as long as they don't rush in let's say the restaurant I'm eating in and sit down naked by my side. LOL
I remember once when I was strolling along the beach with some older relatives and I suddenly saw an old man approaching: I soon noticed he wasn't wearing trunks. Despite I got embarrassed and blushed while quickly looked away, it didn't traumatize me in the least. I'm not saying I don't understand it when people don't wish to see other people naked, I myself prefer non nudist beaches and people with some clothes on the streets, but still I don't care a bit what kind of dresses they choose to wear. What's more, I once saw a man in London who was wearing a hospital gown which was all open on the backside and you could perfectly discern his butt... and no one seemed to even notice it. I just found it odd and funny.
I think most people who are so concerned about what others wear or who they go to bed with have some kind of inflated ego issue.