Same Sex Marriage and Polygamy

I'm no expert on the same sex marriage platform, so set me straight (no pun intended) if I'm not accurately representing their position. My instincts tell me that monogamy is not a tenet of the SSM movement. An initial internet search yielded this interesting website devoted to this question.

My hypothesis is this: monogamy is not important to SSM advocates. How do I come to this conclusion? Well, for starters, monogamy doesn't appear to be a plank in the platform. Second, SSM advocates often use infidelity and marriage failure rates among heterosexual couples as an argument in favor of SSM. The rationale is that heterosexual couples have done enough damage to the institution of marriage that SSM won't make any difference. This reasoning is often used against traditional marriage advocates, who generally believe that SSM will destroy the institution of marriage. My biggest reason for opposing SSM is that it would allow public schools to teach the next generation that SSM is normal. I believe SSM confuses children, frustrates the family unit, and has irreversible negative social consequences, but that's a topic for a different blog.

My point is this: SSM advocates claim that marriage is a right that should be extended to homosexuals. They base this on the fact that marriage is a legal arrangement between consenting adults. If I have framed their argument correctly, then in order to remain logically consistent and to strengthen their argument even further, SSM advocates should actively support plural marriage as well. Proposition 8 provided California with a definition of marriage: the union of one man and one woman. The objection from SSM advocates focuses solely on the issue of gender, not on the number of participants. If marriage is a right that consenting adults are entitled to, and if monogamy is not a stated ideal, then they should have no problem with institutionalized polygamy. Yet SSM advocates avoid the plural marriage issue like the plague, and they are smart to do so because they understand the stigma associated with polygamy. Their silence on this question is understandable, but I would love to hear an SSM movement representative provide a clear and unequivocal statement on polygamy.

A June 2006 article in the Weekly Standard included some interesting conclusions on polygamy by Stanley Kurtz, a fellow at the Hudson Institute. He was grieved at the arguments of modern intellectuals who support decriminalizing polygamy. Kurtz concluded, "Marriage, as its ultramodern critics would like to say, is indeed about choosing one's partner, and about freedom in a society that values freedom. But that's not the only thing it is about. As the Supreme Court justices who unanimously decided Reynolds in 1878 understood, marriage is also about sustaining the conditions in which freedom can thrive. Polygamy in all its forms is a recipe for social structures that inhibit and ultimately undermine social freedom and democracy. A hard-won lesson of Western history is that genuine democratic self-rule begins at the hearth of the monogamous family." While I tend to agree with his conclusion, it doesn't really demonstrate the nexus between polygamy and the undermining of freedom/democracy.

So I ask...if it's really all about consenting adults, on what basis can one support SSM and oppose polygamy?