This is a non sequitur. << before the issue gets lost in the language, best I amend my previous statement to be more elucidatory, and thus say: "However, marriage in it's very definition is (an undertaking of committment) between two individuals. So at it's very core, marriage is meant to monogamous.
I think the logical conclusion is that if marriage is between two individuals, it is what those two individuals decide it to be; unless of course there are set or presumed cultural expectations and demands laid down within the contract, religious or otherwise.
All that I have been saying is that your religious and cultural expectations are that it will be monogamous, in every sense of that word, yet clearly the reality of people's behaviour is at odds with this.
I don't recall anyone (any posters) being against polygamy, but rather against the concepts of cheating, betrayal and lack of consideration for the other party to the relationship. i.e.: the sentiments are morally and ethically driven and not culturally or religiously. If I were to break it down even further, I'd say people can boink whomever they want, just stay away from people who are in relationships/married which are not open or allow for such activity.