"So how much of homosexual exclusivity is due to the hetero-majority's bigotry that segregates gays, for example?"
So you're basically saying that homophobia wiped out our potential or existing bisexuality and hardened our straightness/gayness?
I think Speedo thing became an issue in the 90's. You'll notice now that it is mostly middle aged men and older who wear Speedos.
Speedos are sexy but they're said to be TMI and then there's the pubic hair poking out!