I also think it's off-base to interpret homosexuality as a complex of sex acts only or primarily, despite the unfortunate construction of the word and of the phrase 'sexual orientation'. It also makes me wonder how the people making these sorts of arguments see their own (presumable) heterosexuality. Let's please not use the hydraulic model if we can avoid it.
Human being, like other animals, have a reproduction drive that is larger than a pleasure drive. The "nesting instinct" for instance is not pleasure-oriented. The reproductive drives of males lead them to prefer sex with younger females even though sex with the somewhat older females is apt to be technically better. Their reproductive drive leads them to prefer sex with ovulating women over those that are not, even if they don't see pregnancy as a desirable outcome. The feeling women have that "their biological clock is ticking" is about reproduction, not pleasure.
The reproductive drives of heterosexuals leads them to reproduce in large numbers. The same cannot be said of the reproductive drive of the average homosexual.
So what?