Actually I come closer to being convinced by this one here, at least for the general case in favor of transcribing taboos into prohibitions.

That links to this comment. Which argument did you mean?

I do note that both the Popenoe passage linked earlier and the observation that "the taboo against homosexuality" is extremely common across cultures" run counter to some of the evidence

The relevant period to look at would be the modern era (post 1500), when new advances would screen off the apparent connection between old taboos as their function. And in that period, it is significant that populations making up most of the world, depsite separation and diversity in other areas, had such a taboo. Yes, places have relaxed taboos since then, but they were all taboos that had a long origin.

And that there is plenty of evidence that this and similar taboos, when enforced, are enforced hypocritically.

What do you mean "hypocritically"? Homosexuals enforcing the taboo? I'll assume you meant "inconsistently", in which case I still think you're not addressing the conservative argument. Of course their enforcement will look inconsistent, because it has long been detached from its original change-in-taboo/consequence feedback loop (like the woman who follows the family tradition of cutting off the ends of a turkey without realizing that the tradition only began in order to be able to fit it into the first generation's small oven).

Nevertheless (the conservative argument goes), you still need to be able to identify the need the taboo filled and its interplay with the other social mechanisms before justifably concluding it's time to end the taboo.

So, I ask you: Do you accept that a culture has to be pro-reproduction to avoid memetic overload from cultures with different values? If so, what would be the limit of the taboos/prohibitions you would want for achieving that end, given the resistance people will put up to different kinds of laws? (e.g. why not make use of people's existing ick-reactions?)

Just to clarify, I'm not defending laws against homosexuality, just pointing out reasonable concerns that underlie the (unjustifiable) prohibitions, since you asked.