Interesting thread.
As far as gay being a choice or not, the opinion I seem to be forming is that it is a mixture of both. It seems to me that some people are born with a genetic defect that predisposes them to have traits of the opposite gender. And some gays are no doubt influenced by current culture or feel scorned by one gender of person and want to try another, or whatever.
There are many instances of gay people having sex with the opposite gender. 93 percent of women who call themselves lesbians have had sex with men. 93 percent!! And yet it is not a choice??? Who or what you decide to make love to is always a choice.
Here is where I got that stat from for you proof people out there.
Katherine Fethers, Caron Marks, et al., “Sexually transmitted infections and risk behaviours in women who have sex with women,” Sexually Transmitted Infections, 76(5): 345- 349, p. 347