I think the reason for the high numbers is the barrage of crap on TV and the rise in numbers of (straight or gay) what I consider weak effeminate men and their attitudes. (Largely due to dad not being around)
Gays run the entire entertainment industry, and if you want to stay in the business, you’d better tow the party line. Charlton Heston once said, that there are more closet conservatives in Hollywood, than closet homosexuals.
I wouldn’t discount the real possibility that most americans have no idea what “percent” really means, and think that 20% sounds really low.
There is a gay guy at my wife’s work. So far as I can tell, this is the first gay person she has ever really known (I’ve known a few, and worked with a few).
I would bet that if you asked most people what percent of people they KNOW are gay, the number would be extremely low. I just think people are stupid when it comes to measurements and estimations.