Here's my agenda for promoting homosexuality:
Write people as people.
Sex permeates our lives from just before puberty until death.
In the far future we depict we have multiple species, some with only one gender, some with "extra" genders and with a wide variety of sexualities within each. Not to mention inter-species romance of the non-humanoid kind (Medusan/human anybody?).
To me this whole "Who's having it off with whom" stuff is a bit juvenile.
People have sex. In Trek world, we have to assume, along with our gender, faith and ethnic prejudices being put away, sexuality would not be the issue it is for us now.
Sex permeates Sword of Damocles. Procreation, sexual attraction, romantic love, lust, to me these are the primary axes around which life revolves.
And that means hetero, homo, bi, tri, quad, omni, multi, inter, whatever. All of it is in play.
Loolooa Tereshini is, for instance, a sexually mature female of her species who has both male and female parters. Does that make her bisexual? She's not even human. Who knows what permutations she's used to? Not me.
Xin Ra-Havreii is what I call an "aggressive hedonist." Natural for his species. A bit much for a lot of humans. Is he therefore amoral or immoral? I don't think so. He simply is.
I doubt the word "gay" is even used to denote homosexuality in the Trek future. No more than anyone would refer to me as black. I'd be "human" (or "brownskin" if you were a pissed-off Andorian).
Which is sort of the whole point.