I don't think Star Trek is. The trouble is Gene Roddenberry's underlying message that people's differences are no big deal and are accepted to the point where there's absolutely no need to say anything. That sort of goes against what it is to be homosexual in the 20th/21st Centuries. TV and film is largely full of attention seeking gay characteratures who fall into common stereotypes - largely femine bitchy types, obsessed with musical-theatre, in many cases promoting promiscuity and unable to have lasting relationships because society frowns on same sex marriages. Producers pander to those worst aspects and rarely create any positive role models, to counteract the homophobia out there.
I don't know so much about American TV, but judging by British programming I don't have much confidence a gay character on Star Trek would escape falling into that trap. Having to meet audience expectations of what gay and lesbian people are like... which unless you work in showbusiness, I presume doesn't bear too much relation to those out there living ordinary lives.
If Star Trek had moved with the times and for instance, during Enterprise had given us a gay crew person... I'm happy to admit as a hetrosexual fella that wouldn't have changed a thing for me. I'd have still have watched it week after week and been disappointed when they cancelled it. I think the character who mostly likely would have fitted this would be Malcolm Reed. That could have worked without alienating what was (correct me if I'm wrong) a core male audience. Specifically a character with a macho interest, his role as Armoury/Tactical Officer and he wouldn't have been obvious, until the occasional storyline discussed it... Plus with T’Pol, Hoshi (straight guy interest), Archer, Trip, Mayweather (straight female interest) it probably wouldn’t have changed the dynamic between the cast. As it turned out, the writing didn't go there with Reed (or any other characters) for whatever reasons and he was written with straight romantic interests... mainly that 'Shuttlepod One' fantasy involving T'Pol and to make him occasionally uncomfortable around her and Trip.