A reader writes:
I'm guessing I must be email #121,981 on the subject, but the Trekkie in me persists. J.J Abrams is not only wrong, he is being disrespectful of the long history of Star Trek. He's also late to the game; this clip, in which two female characters kiss, is from a Deep Space 9 episode that aired in 1995.
That clip is unembeddable, but the scene is contained in the above compilation, which "deal[s] with issues of same-sexuality or 'alternative' sexuality" in Star Trek. Another reader digs deeper:
Star Trek has already broached the subject of same sex relationships more than a decade ago, albeit after two notable failures (and the 'success' involved two attractive women kissing, but it was the '90s). First, there was the character of Elim Garak from the 'Deep Space 9' TV series, one of the major characters and initially portrayed as something like an omnisexual, who was openly attracted to the young doctor Bashir character until the studio put the kibosh on it.
Andrew Robinson provided non-canon insight into his role when interviewed by Amazon.com, stating "I started out playing Garak as someone who doesn't have a defined sexuality. He's not gay, he's not straight, it's a non-issue for him. … Originally, in that very first episode, I loved the man's absolute fearlessness about presenting himself to an attractive human being. The fact that the attractive human being is a man (Bashir) doesn't make any difference to him, but that was a little too sophisticated I think. For the most part, the writers supported the character beautifully, but in that area they just made a choice they didn't want to go there, and if they don't want to go there I can't, because the writing doesn't support it."
However, the more relevant attempt was taken during an episode of 'The Next Generation' wherein the android officer, Data, attempts to build another android in his image with the aim of better understanding his own humanity through the act of parenting and guiding another, less-experienced being, through the difficulties of understanding humanity. The relevant scene takes place in the bar onboard ship, where his child has become a waitress and asks Whoopi Goldberg's character why couples are kissing.
In one of the scenes with Guinan tutoring Lal about human sexuality, Whoopi Goldberg altered one of her script lines in order to turn a strictly heterosexual explanation into a gender-neutral version: "According to the script, Guinan was supposed to start telling Lal, 'When a man and a woman are in love …' and in the background, there would be men and women sitting at tables, holding hands[...] But Whoopi refused to say that. She said, 'This show is beyond that. It should be 'When two people are in love.'" It was also decided on set that the background of the scene show a same-sex couple holding hands, but "someone ran to a phone and made a call to the production office and that was nixed. [Producer] David Livingston came down and made sure that didn't happen." (TNG research assistant Richard Arnold) 
This is all obviously a bit irrelevant to the point of showing an openly gay character in a new blockbuster motion picture which takes place in an idealized future, but the point remains that it wouldn't be the first time that the subject had been broached. And Ryan's point is spot on as far as the history of the franchise goes with regards to homosexuality in the future.