Interesting one, although it is hard to give full diagnose as question is rather complicated. Socialization has the biggest impact and it can't be denied. Homosexuality exists ever since,  and it is nothing strange or wierd about it, but these days it became like mainstream movement. Being "different" is the ultimate guide, even if it means to change your sexual orientation. I hope noone will get offended but mostly people choose to be gay in order to get attention they mostly desire. On the other hand there are people who were born that way and i'm fine with it as they do not directly affect my life. The only thing that matters is are you a good or a bad human being, after all we should all be united in diversity. Cheers