Tut tut, if you don't like nBSG, get out of this thread. Or prepare an intelligent and respectful counter opinion relating to the themes in this thread.
As for sex for the fun, the rightness, of it being "gratuitous", then you could say that for anything. Jokes between Spock and Bones are out. Conflict between aliens too - after all, how titillating it is, the possibility of interstellar war that will likely kill billions. And we've dipped into that well with Klingons and Romulans and Cardassians and Tholians and Talarians and Jem Hadar and Gorn and Breen and so on over the course of, what, a century in-universe?
But like I said, sex for the right reasons isn't really found in entertainment nearly as much as for wrong reasons or even for neutral easy reasons and that makes it rare and interesting. How good can it be? Tell me, sci-fi writer, if you dare.
And watch viewer if you dare. I wonder if the true "geeks" in the sci-fi audience aren't holding the genre back b/c they don't get as much "physical intimacy" in its myriad forms as general audiences, and if general audiences aren't holding exploring the unknown possibilities of healthy relationships (and specifically to this thread sexual ones) back b/c they, because we all, have become unsatisfied neurotics about what was supposed to be the most natural thing in the universe. I think we're bad at relationships and in denial about sex so in art they have to be dysfunctional and it verboten.