So are a lot of places where heterosexual, monogamous marriages are normalized; are we using a reasonable comparative measure? I'm not sure I would list the Roman empire as a time of spectacular achievements in gender relations.
I mean, are we suggesting that a decent, kind, loving father, upon acquisition of an additional wife, suddenly becomes a brutish thug? Or is this just code for "we hate Mormons and Muslims, and therefore connect our stereotypes of them to polygamy in general"?
I've gone over this subject before, so I'll just refer you to my other posts on the subject:
http://www.religiousforums.com/threads/polygamy-your-thoughts.185384/page-2#post-4668581
http://www.religiousforums.com/threads/should-we-legalize-polygamy.178922/page-4#post-4732896
It has nothing to do with religion, in my eyes. I go by research and the effects on society it would likely have. I'm opposed to polyamory, too, for much the same reasons and that's not associated with conservative religious people. I certainly don't hate Mormons and/or Muslims. By the way, only tiny fringe Mormon sects practice polygamy now.
I also didn't mention the Roman Empire in terms of being "a time of spectacular achievements in gender relations". I mentioned Rome because:
"...socially imposed monogamy was first established in ancient Greece and Rome, centuries before Christianity even existed. Greco-Roman laws prohibited any man from having more than one official wife at a time. It's true that forms of de facto polygyny (e.g. concubinage, sex with slaves) continued to be tolerated in these societies. Nevertheless, anti-polygyny laws made Greco-Roman society relatively sexually egalitarian (Scheidel, 2009), because by preventing elite men from legally acquiring multiple wives, they improved the ability of lower-ranking men to acquire wives of their own.
So by the time Christianity began spreading through the Roman Empire in the first centuries AD, monogamy was already well-established. But even though Christianity did not introduce socially imposed monogamy to the West, it did fully embrace this institution, and as noted above, it was this embracement that ultimately led to monogamy's spread throughout the Western world."
https://www.psychologytoday.com/blog/darwin-eternity/201109/why-we-think-monogamy-is-normal
See also:
https://en.wikipedia.org/wiki/Monogamy#Ancient_Greece_and_ancient_Rome
This is interesting, too:
"Western European societies established monogamy as their marital norm.
[64] Monogamous marriage is normative and is legally enforced in most of the world's highly developed countries.
[65] Laws prohibiting polygyny were adopted in 1880 in Japan, 1953 in China, 1955 in India and 1963 in Nepal.
[65]
The
women's rights movements in these nations want to make monogamy the only legal form of marriage. The United Nations joined these efforts in 1979 when the General Assembly adopted the
Convention on the Elimination of All Forms of Discrimination Against Women, an international bill of rights for women that over 180 nations have agreed to implement. Article 16 of the Convention requires nations to give women and men equal rights in marriage. Polygamy is interpreted as inconsistent with Article 16 when it extends the right of multiple spouses to men but not to women. The United Nations has established the Committee on the Elimination of Discrimination against Women (CEDAW)
[66] to monitor the progress of nations implementing the Convention. The United Nations is thus working through the Convention and CEDAW to promote women's equality by making monogamy the only legal form of marriage worldwide."
So unless you can find research into the subject that shows that polygamy that can lead to positive social outcomes for women and children, I see no reason to support it. The evidence seems quite clear that societies that have normalized monogamy over polygamy function much better in general, with better outcomes for all concerned.