And Bugs Bunny married Elmer Fudd in the 1950 cartoon "The Rabbit of Seville". Of course, the consummation consisted of him dropping Fudd into a giant cake with "The Marriage of Figaro" frosted on it.
Jokes aside, yes, some shows crossed the line decades before Trek (first same sex kiss, 1995, first gay character was Sulu in the reboot, over a decade after). But remember also that in some states, it was illegal to date a member of your own sex until 2003, and the laws were not repealed by the will of the people in those states (but by the Supreme Court deciding that what consenting adults do in the bedroom isn't the state's business). So obviously, in the 90's and early 00's, there was still a strong opposition to same-sex romance. Indeed, I work in a liberal district in one of the bluest states on the Union, and I still regularly have to deal with kids making homophobic comments, the same stuff I remember hearing back in the 80's. And if it's still around today, after decades of concentrated efforts by the media to eradicate it, think how much stronger it was back in the 90's, just a few short years after the AIDS crisis. This might have been a dragon that Rick Berman wasn't willing to risk starting a fight with.
With seperate beds, though. Not sure that totally counts.