Stein's theory that gay sexual orientation is probably not biologically determined is not supported by most gays. A 1995 poll of Advocate readers revealed that three quarters of the respondents are convinced that their sexual orientation is indeed determined by genetics. Who is Stein to say these lesbians and gay men do not know the reality of their own existence?Three quarters of Americans believe that they are above average, but that doesn't mean they are. According to this site, 69 percent of American men believe that they are physically fit, while only 13 actually are. For that matter, six out of ten Americans reject Darwin's theory of evolution; who am I to say that these people do not know the reality of their own existence? (No monkey ancestors for them!)
No amount of introspection can tell you that anything about you is "determined by genetics." That's something that can only be settled by research into genes and what they do. At present, it is pretty clear that homosexuality is not determined by our genes; if there is any genetic influence at all, no one knows what it is. But whatever may eventually be discovered, it won't be settled by opinion polling.