One argument that’s often made against legalized polygamy is that rich old men will marry lots of women, leaving lots of poor young men both single and sexually frustrated—-and that’s bad, because poor young single sexually frustrated men are prone to criminal acts of violence.
Over at Overcoming Bias, Robin Hanson objects that if people really believed this argument, they’d want to criminalize lesbianism and extramarital affairs, both of which also contribute to the problem of men-without-partners.
But I think one could consistently take the position that while lesbianism contributes to the problem, it’s just not widespread enough to be worth stamping out, while polygamy (if legal) might well become so. And as far as extramarital affairs, I think Robin has it completely backward: When the wife of a 30 year old man (who is well past the prime age of violence) has an extramarital affair with an 18 year old, she is alleviating the problem, not contributing to it. Besides, most extramarital affairs do not deprive the husband of a long term sex partner.
I’m all for legalizing polygamy, because I’m all for legalizing almost everything. But I don’t think you can dismiss this argument—or the sincerity of its proponents—as easily as Robin seems to think you can.