Well you're so abrasive about it, like unreasonably so...Also "designed", do you believe in a god? If you're Christian then I don't believe we need to discuss futher, also do you carry a different attitude towards gay people? Something others would call prejudice? You realize the human race is stable enough at this point that having a few gay people would be benefitial to the population increase?
No, the brain is actually just fine, that's like saying people who are left-handed have a brain not in working order, it's merely a different shade of a color. You realize it's not impossible for a gay man to father children right? Being gay doesn't turn off your testicles or ovaries...It's just not your personal preference to have sex with the opposite gender.
If you think sex without reproduction is fine then why are gays "wrong" for doing what you consider "ok"? You argue that having a condition such as homosexuality that hinders your reproduction is wrong, but having sex for recreation is ok? Broken is a pretty harsh term to use by the way. It's not like having a cold, it's someones identity.
Your argument, what does society lose by having a few gay people? Why are you so strongly defending this idea that gay people are "broken" even though in today's society it doesn't matter, as in, our population is stable, we don't need more babies and they don't hurt anyone.
I do disagree actually, you're providing a scenario without some kind of history, what's the cause of the mass homo/hetero sexuality in each world? If it's evolutionarily dictated then obviously it would benefit reproduction, if not, then I'd argue humans are not stupid, if the fate of a species is an issue then obviously people would reproduce merely to save it. You're scratching the bottom of the barrel merely to fuel this debate over semantics and personal identity while failing to see it's impact on modern society, which overall pretty neutral because again...we don't need more babies, a modern society such as ares doesn't need to be held up to this prehistoric notion of "what's natural".
If it doesn't hurt anyone, why do you regard it with such harsh terminology? Why is being gay, where you can infact reproduce if society needed it, worse than being infertile or sterile?
Do you believe gay people deserve the same rights as straight people? (not marriage, you mentioned that earlier)