I'm sure there will always be an initiative to continue the human race. Of course you're giving rather vague hypothetical situations seeing that I can highly doubt seeing a world with only Gays and Lesbians as opposed to one world where everyone is assumed Heterosexual. We also have technology, and with that we have sperm donor banks and artificial wombs. Also Gay and Lesbian couples would want to seek children to raise, so their option is sperm donor and artificial wombs, etc. You can call this unnatural I suppose, but it is possible in your hypothetical example.
But I'm rather confused with your objective approach, you claim those that are inclined to love someone of a gender or person that is incompatible of engaging in reproductive intercourse is broken. But what if sex is not the main component in a relationship? I know I see it that way at the moment, I rather just love someone for who they are and not get involved with sexual intercourse. Do I control that though? Most likely not, I cannot force myself to have sex if it does not appeal to me. Does that qualify me as " broken " ? Maybe if someone was a Eugenicist and looking for the able man and thought that sure, not to point fingers at you though.
Truth is, we all have these odd subjective standards of what is " broken ", as Stryker has stated, Humanity has many broken elements that most of us can't control or we voluntarily engage in. Someone with Autism may have some mental deficiencies, but does that make them broken and not perfect? After all, many brilliant scientists and mathematicians had Autism and the like and outnumbered many groups of non-Autistic academic individuals, but even them too are not broken because they cannot grasp the high standard that these Autistic intellectuals have.
So really, even if you think many of us are " broken " because either we cannot reproduce to save the worlds population and continue what mother nature had created for us, what about the other natural aspects of humans? What about discrimination? we are naturally prone to choose one over the other, but we cry out to others to stop discriminating because it is immoral, or what about our rather repulsive greedy reflexes us humans have? we are born with free will and self-determination and we have our own self-interests even if it results in greed that affects others. Would we be broken for not discriminating or choosing not to be greedy since it is out of line of what humans tend to do? Just like reproductive intercourse, even though we are built to have the opportunity to do so, are we supposed to under natural standards? I guess that depends on the individual's self-interest of how the natural mind and the natural environment molds.
Of course I'm not offended by your remarks, don't get me wrong. It neither picks my pocket nor breaks my bones. But I just wanted to get my popular opinion out to shed another perspective on the matter.