Years before I came out, I read books featuring homosexual characters. No, I was not reading Gordon Merrick novels. There is a genre of writing which generally acknowledges the existence of queers and even integrates them into its fabric.
When I was in eighth grade in 1980, I read Thomas Disch's "On Wings of Song." The science fictional premise of the book is that with the aid of an electronic device, a person who integrates the hemispheres of their brain through song can astrally project, becoming what the book calls a "fairy." The main character of the book eventually becomes the kept boy of a castrato opera singer.
Another piece of queer science fiction I read around that time was Tom Reamy's short story "Under the Hollywood sign." In it, a cop becomes overwhelmed by sexual feelings for beautiful inhuman clones he sees at the sites of deaths and eventually captures one, whom he chains to a bed and repeatedly rapes. The story was written in about 1975 (and doesn't it remind you of the 1980 movie Cruising? For that matter, the Basket Case movies appear to be derived from his short story "The Detweiler Boy") Reamy died young, in about 1979. Harlan Ellison is still sitting on an unpublished Reamy story, which he has been holding for the past 20 years for his will-it-ever-appear anthology, The Last Dangerous Visions.
Unforunatly, one opportunity to warp myself which I missed during my adolescence was reading Samuel Delany. It wasn't until adulthood that I read his depictions of queer anarchist utopias. I was scared off earlier, I suppose, by warnings of the "difficulty" of the experimental Dahlgren. Don't let anything stop you from reading this classic.
Queer characters exist integrated into the worlds of much science fiction writing -- Dreamsnake, the Darkover books, etc.
Although I did not overtly identify as a homosexual in highschool (sure I jerked off but I was otherwise fairly asexual) I feel certain that these books helped nurture a self-acceptance that came to rapid fruition a few years later.
I think that the openness towards homosexuality (or perhaps more correctly, polymorphous perversity, since that is the quality frequently present in science fictional utopias) is mirrored in the world of science fiction fandom (though which is the original and which the reflection is impossible to determine.) I was never a participant in the organized form of fandom (though I would have been if not for an overprotective mother who felt it was wrong that someone my age would associate with adults with such a juvenile interest as science fiction. Clearly these were some sort of perverts.) Most of my few friends in highschool shared my interest in science fiction, and though I think that some of them have since also shared my other proclivities, at the time they were also apparently asexual.
I think that science fiction, like punk, attracted me because of my sense of differentness, my longing for an escape from the mundane world in which I had no obvious place.
Who is carrying the queer SF torch today? I am not so attuned to the current SF scene. Most of what little SF I still read is in the het male dominated cyberpunk arena -- though in this genre, there is queer content such as in Laura Mixon's "Glass Houses," which features lesbian waldo jockeys and Jonathan Littel's queer junkie skatepunk cyberpunk novel "Bad Voltage." And there are gay characters in John Shirley's "Three Ring Psychus" and Gibson's "Virtual Light" (how, after all, could you write a SF story set in San Francisco without a gay character?) And there are publishers like Circlet Press, which publishes queer science fiction.
I'm sure there are latent (or blatant) teen queers out there today discover other worlds through science fiction.