Human sexuality was created as a field of study by people who have psychological issues with sex.  Guys like Kinsey, for example.  It's been hypothesized that all fields of psychology are the result of people with psychological issues trying to diagnose themselves, and that psychology attracts students who are dealing with their own psychological issues.  So it's no wonder that homosexuals are well-versed on how psychology can affect basic understandings about male/female and reproduction.