The state's interest in marriage is stability. Generally speaking polygamy does not work for stability. Inherent in the whole polygamous movement is a deep and abiding misogyny and denigration of women. So polygamy is objectionable on lots of grounds.
You know what I really love? The CD players in a car. How when you put the CD right up by the slot it actually takes it out of your hand like it's hungry. It pulls it in and you feel like it wants more silver discs.