No practice that results in such ill effects should be a “right” under the US Constitution.
“The harms flowing from polygamy are too evident to ignore and too serious to allow to occur under the guise of fundamental rights.” (Lawyer, Thomas Buck.)
Is the polygamy issue “just like gay marriage?” Gay marriage and polygamy are vastly different in effect. We do not see the same abuses in monogamous, same-sex relationships. Gay marriages potentially offer equal power sharing and a stable unit that is not constantly changing with the addition of new partners.
Consenting adults? Many adult women enter polygamy under psychological and emotional pressure, believing that their eternal souls are in danger of destruction if they refuse to participate. Women from fundamentalist, Muslim, and other backgrounds face cultural pressures to conform to this practice.
Legislating morality? The US has always “legislated morality” independent of any religious rationale. Murder, rape, theft, etc., are illegal because they are morally wrong—i.e., they cause significant harms to individuals and society. The same applies to polygamy. Its results extend far beyond the bedroom.
“Good” polygamy versus “bad” polygamy? Canada’s ruling on polygamy found that “The harms associated with the practice are endemic; they are inherent.” This means that the harms of polygamy are not just the result of abusive individuals. Social, physical, or emotional harms are inevitable where polygamy exists.
Equal rights. Polygamy violates a woman’s right to equality and emotional health. Polygamy is “anathema to women’s economic, social and emotional well-being.” (Dr. Shoshona Grossbard.)
Disrupted family stability. In polygamy, men compete for women while attempting to maintain multiple relationships. This forces women to compete for love, attention, and resources. It also restricts time available for parenting and diminishes the economic resources needed for children’s well being. Living in a family where the dynamics may change at any time as the father adds multiple partners, creates insecurity for children and family instability.
Women as a commodity. Polygamist males frequently seek to control the lives of females, who become commodities to be trafficked and traded between families and communities.
Increased sexual abuse. Holding out HELP (a Utah-based nonprofit) reports that over 90% of its clients leaving polygamy are victims of physical or sexual abuse (of which incest forms a part). Illegal underage sexual relations occur more frequently because competition for females drives down the age for “marriage.”
Polygamy, an antisocial and unsustainable practice. With a global 1:1 ratio of men to women, polygamy permits some men exclusive rights to multiple women, while denying other men a partner. One example of this anti social behavior is the “Lost Boys” phenomenon. In nations where the gender ratio has been disrupted, sexual violence follows. (See India, where selective abortion of females means some men cannot find a partner.)