You seem to have posted this in two places so I'm going to copy my response here:
It's interesting that folks tend to wonder about the Mormon point of view when they hear of polyamory, but it isn't actually the same thing. Polyamory
is the practice, desire, or acceptance of having more than one intimate relationship at a time with the knowledge and consent of everyone involved. Polygamy
is a marriage which includes more than two partners. The Mormons at one point believed in the latter, but now only Fundamentalist Mormons do so. Learning more about their beliefs, however, I realized that the basis of their heaven still allows for polygamy in the afterlife, as those who make it to heaven are reunited as a family with all of their married Mormon partners from this life.
From my point of view, it's hard to agree with the Mormons on most things. This is because I spent a year attending their church and realizing how demoralizing and genderist their society is to women. When it comes to polygamy, I simply can't condone the manner in which most of their polygamist relationships were (and are) run. They aren't based on mutual consent and love as much as they are men claiming power over women and forcing them into a submissive role.
Not every polygamist relationship is this way, but the majority through time have been and I can't accept that. Especially the communities in which women as young as ten were forced to marry older polygamist members of the sect.
I believe in polyamory because it involves mutual consent and love on the part of all partners. It's not a power trip unless everyone wants it to be, and it doesn't interfere with people's lives in an illegal and immoral fashion. If polygamy could be tailored this way through education and proper power balance, then fine. But the point is it's not. And I just can't be okay with that.