I don't care who anyone else marries, so long as they are entering that marriage on their own free will.
With that said, I think the issue for me lies within the legal issues it could create. What would this mean for immigration? Can a man marry x amount of women to bring them into the country? What about divorce? What happens with custody of children (seems simple, biological mother and father but can you imagine) , assets, etc? What about benefits? Tax breaks? There would have to be a large change in the legal aspect of marriage.