A fair question

According to the NYTimes, Warren Jeffs, leader of a schismatic Mormon cult that adheres to the doctrine of polygamy, is to be tried in St. George, Utah, on charges of accomplice to rape for his role in arranging marriages between older men and underage girls. Seating a jury will pose interesting problems, as St. George is full of orthodox Mormons, who long ago delegitimized multiple marriage as a dodge to get statehood.
Article reads, in part, “Amber Clark, 28, an Army veteran who moved here from California about two months ago and who described herself as an active Mormon, said she thought polygamists should be left alone, so long as no one was under age or coerced into marriage.
“’I’m liberal in that respect,’ Ms. Clark said. ‘If it’s legal in some states for people of the same sex to get married, why is it not legal to marry more than one wife?’"
So, how do you think advocates of gay marriage would come down on the question of polygamy? My gut feeling that they would oppose it, but I'm not sure why I suspect that. Perhaps an equitable solution would be to institute some sort of civil-attachment registration for any bond that doesn't include animals, children, or coercion -- quantities and gender of no weight. Let 'em call it what they want, no religious sanction express or implied, and, please, don't tell me about it, cuz I'm really not interested.