I appreciate the civil conversation as well.Thanks for a civil discussion on the topic.
There wouldn't.If same sex marriage were accepted, what would be the problem with extending this to any relationship between any number of consenting adults?
There is nothing inherently immoral, or un-spiritual with polygamy. (Insert joke: I've got enough problems with one wife on my hand... <rimshot>) I don't think it's good. Or the best. But you can't make a biblical case to enact laws requiring that the state only recognize "marriage" as between one man and one woman. It can just as well be between one man, and two women.
And also, without spending days researching the subject, and admitting my fallibility, I believe that the justification for the anti-bigamy laws were in large part religious persecution of Mormons.
I believe you are making a slippery slope argument that once (the state) lets this group (male/male, or female/female) marry, then what is to stop other combinations (male/male/female or male/female/female) or (man/dog.)
My answer to that is that the state needs to make its decisions balancing the common good, with religious freedom. It would be impossible to win a court case determining that a gay or plural marriage was bad for society based solely on the premise that gay = bad, or plural = bad. The only way to invoke that is with religion, which is then violating religious freedom. By contrast, a judgement could be brought against a specific marriage or other living arrangement on a case-by-case basis, that was harmful to any of the parties, including children. But the criteria would be the same regardless of same sex, heterosexual, or plural. Neglect. Physical or emotional harm to any of the parties, including themselves. But this is no respecter of race, creed, or sexuality. We are capable of great harm to each other. But not because of who we love.