And there's a point where you're verifying so much that it becomes impossible to progress a discussion. For example, can you give me some statistic on how often things that make sense don't hold true when tested
Often enough that we've had years of scientific progression
"Oh shit, logical deduction based on previously accepted axioms failed in the face of reality" is pretty much one of their major kickoff points. It's especially common in the social sciences, yeah, though a lot of that is due to how young the field is.
If you'd like something more grounded in logic, the rebuttal would be that 'people enjoying heterosexual sex' doesn't necessarily entail 'will have more children.' Pretty much nobody enjoys
birth (Debilitating, incredibly painful, and possibly deadly, especially in the past.), after all, so avoiding procreation while having sex is pretty high on a lot of peoples lists, and has been for a very, very long time. All you get from 'people enjoy sex' is that 'people will have more sex if possible' (assuming the axiom that people seek what they find enjoyable; something that isn't always true), not that they'll breed more. You also seem to be ignoring that social pressure to reproduce may be capable in itself to keep the homosexual population reproducing
enough, assuming that the presumed genetic trait stays strictly within homosexual individuals (which I'm fairly sure pretty much no one has basis to claim. Implicit: And no be pulling it out of their proverbial arse.). If the trait is recessive or rides on something else within the larger population, reproduction within the homosexual population is entirely likely to be completely irrelevant.
What I'm basically saying is, that while what you're saying
may follow logically, you're making jumps you can't back up without unfounded conjecture. Considering you're making testable claims, that's kind of a deathblow for what you're proposing.
For some subjects there are simply no available studies. So unless you're gonna finance one, we have to settle for conjecturewaiting until there is one.
Incidentally, I've shifted that for you. When we're talking things that can influence policy or peoples actions in very meaningful ways, that's the direction you need to go.