I've been reading several articles recently claiming polygamy will sooner or later be legalized in the United States.
It won't. And that is very good thing.
One of the main reasons why it will not is that when one man can monopolize many women some of the remaining men will turn to sex with pubescent and pre-pubescent boys. If you do not believe this will happen all you have to do is look at the Islamic world.
If polygamy was legalized in the U.S. some men would start paying for young boys. They do already. There are unfortunately men out there (and women) who like sex with children, pre-pubescent and teenage boys. There is large industry in some of the poorer Asian countries serving these perverts.
The first time I ran across these practices was in James Michener's novel about Afghanistan, The Caravan, which had graphic depictions of the "dancing boys" that men would murder over. One man murdered another for a boy, then he paid for it by having his head sawed off with a rusty WWI bayonet.
It's bad enough that under polygamy 16-year-olds boys can be tossed out on their own (which happened in a polygamous Mormon community in the U.S., until the Feds closed it down) or that ultimately we would end up with an extremely stratified society with all wealth concentrated at the top, with those at the bottom having no wives or jobs, but the most horrifying just might be that the increase in the rape and traffic of young boys would be enormous.
These practices might take several decades to work their black magic, but work their black magic they will. It won't just be prostitution but sexual slavery. The Good, the True and the Beautiful this ain't!
You don't even need any thought experiments to figure these things out. All you have to do is look at history. You even need history, for that matter. Just look at the practices in parts of the world that have polygamy.
NAMBLA would love this development.