From past experience I've found that taking an economic/scientific approach to certain things, especially human relationships, is considered a profane act in certain parts of modern day society. Many of my past attempts to discuss the economics of relationships results in accusations of sociopathy for attempting to understand relationships under a transactional framework. I've yet to figure out the cause of such opposition.

That HN doesn't result in this reaction (at least not nearly as strongly as other places) means it is one of the places most equipped to discuss it.

But it is possible for the most equipped place to discuss something to still be woefully inadequately equipped to discuss it. The richest person in a room can still be poor.

I think that's because an acknowledgement that the kind of marriage one selects has an "environmental impact" immediately brings the sacred cow of gay marriage into question.

When it really shouldn't. You still have a fundamental right to select the type of relationship that's right for you, but you do have a responsibility to be mindful of its effect on society. This doesn't just mean ban stuff. Perhaps for polygyny, that would translate into making the relationship non-exclusive, rather than choosing against it altogether.