I don't have a problem with it. I think consenting adults should love who they want. Its none of my concern if there is jeaslosy in someone else's relationship.
What about nonconsenting people (as in the case of the Colorado City FLDS sect)? Girls as young as 12 are forced into plural marrige with men three times their age who already have several wives.
I read both of Carolyn Jessop's books in 2010 (who escaped from this place). Mindblowing, what goes on behind closed doors. There is an extreme amount of jealousy, competition and bitterness between the wives. Wives abuse the children of other wives to try and control that sisterwife. There is physical abuse, starvation and emotional abuse like you wouldn't believe. There is a heirarchy, and whoever is the favorite wife at the time wields power (thru fear) over the others, and the husband believes whatever she tells him, truth or lie.
It was horrible; unbelievable that people are forced to live like this - but in their case they are raised in that religion and system; they are really unaware that the rest of the world does things differently.
On the other hand, there do seem to be some happy polygamist families out there, ones who aren't part of any sect or cult.