I don't recall the details, but does it say that Vulcan homosexuals don't reproduce or (as I thought it was) simply that they are not driven to pon farr
, the mating drive that is orientated to the other sex? Meaning that there is little chance of their procreating unless they choose to produce biological offspring with a member of the opposite sex for that express purpose (since their normal sexual activity is same-sex - and, yes, I know scientific advancement means there's no reason why biological offspring can't be produced artificially for same-sex couples in Trek, which sort of defeats the point, but still). I recall the Vulcan character in question saying that his family were disappointed that he would not be passing on his genes, but was that a statement that "homosexuals don't reproduce" or merely that he had no intent or desire to do so, and since he didn't undergo pon farr
he wouldn't be compelled to mate and do so? It was explicitly the "waste" of good genes that his family considered illogical, I believe.