Reply #32: The word "consenting" gets thrown around a lot here

[Believing Is Art]

and if consenting adults want to have a relationship with one man and many women or one woman and many women, fine, it's their lives. But they can do so without getting married. Legalizing it opens up the door for a lot of trouble.

Man marries woman. She's under the impression it's the two of them for life. Woman has kids, woman gets old and fat. Man marries younger, skinnier woman, because he can. First wife does not approve. Wants divorce, man won't grant divorce because he doesn't want to pay support and alimony, sometimes likes old and fat, still loves her but not her body, etc. This either ends with a lot of lawyer's fees and bankruptcy, or a world of emotional pain for the woman. Everything he did was wrong in the moral sense, but legal. No consent was involved and it doesn't matter.

It could happen the other way around, too, but c'mon. We live in a society that teaches boys to rack up the notches on their bedposts and girls to wait for their prince charming. Legalizing polygamy/polyandry is just making it easier for assholes to be assholes and the wronged parties to be even more screwed.