Well, I certainly agree that the controversial topics you list have the property you describe -- that is, no popular position on them is unflawed.
I don't believe this significantly explains the low light:heat ratio of discussions about those topics, though. There are lots of topics where no popular position on them is unflawed that nevertheless get discussed without the level of emotional investment we see when gender relations or tribal affiliations (or, to a lesser extent, morality) get involved.
That said, it's not especially mysterious that gender relations and tribal affiliations reliably elicit more emotional involvement than, say, decision theory.
There are lots of topics where no popular position on them is unflawed that nevertheless get discussed without the level of emotional investment we see when gender relations or tribal affiliations (or, to a lesser extent, morality) get involved.
The problem is that the positions on this topic (not just the popular ones, but all the conceivable non-transhumanist ones) are not just "unflawed", they're pretty damn horrible, absolutely speaking.
Consider everyone (who's smart enough for it and cares to) unabashedly using "PUA"-style psych...
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.