I believe that if one cannot commit to there spouse one hundred percent, they are ripping the other off. For every person that enters the relationship, everyone else loses more. Declaring love to a spouse is to completely submit to the other. You can't when there are 3, 4 or more as it divides commitment.
If you agree to spend your life with one man and many women then you, instinctivly, accept that when thingsgo wrong you will not complain. You will take any and all punishment simply because you have chosen such an unaccepted way of living. Make your bed and lie in it encourages violence against women.
Polygamy includes polyandry meaning multiple husbands. Furthermore, it's quite possible to have a polygamous family whether multiple wives, multiple husbands, both, even gay polygamy where everyone is treated quite decently.
It does not mean complete submission. It means you love and live together and in a contractual sense it means you share property.
Legal polygamy would be better than just living together. Many Mormon polygamist wives wind up having to live with their husband's brother after he dies because they can't get legal marriage. If they could then the law could require that they inherit the property instead of it going straight to the brother.
The supreme court has said, “The Constitution promises liberty to all within its reach, liberty that includes certain specific rights that allow persons, within a lawful realm, to define and express their identity.” The 14th Amendment guarantees the right to marriage to all citizens, and that denying them marriage robs them of liberty entitled to them by law. Marriage is an ennobling institution that bestows dignity upon those who enter it.
A polygamous or polyamourous relationship is an agreement on all parts. All members of the relationship agree to be in one like that. Just because polygamy exists doesn't mean one person controls all of the spouses. As long as all parties involved are consensual, in the contractual sense it just means that everybody shares property.
Polygamy is a lifestyle and just because we don't live in it doesn't mean we should condemn it for other people.
Back on the topic of it hurting women though, not all polygamous relationships are one man with many girlfriends/wives. One woman with multiple male partners also exists. So do women with multiple female partners and men with multiple male partners.
As long as everyone's happy, how does it matter how many people there are in the relationship?