Only God is the same yesterday, today and tomorrow. The Church has always been changing.
The state's interest in marriage is stability. Generally speaking, polygamy does not work for stability. Inherent in the whole polygamous movement is a deep and abiding misogyny and denigration of women. So polygamy is objectionable on lots of grounds.
I think people often come to the synagogue, mosque, the church looking for God, and what we give them is religion.
When you claim to have the truth, as opposed to the truth as you perceive it, then you move us toward a theocratic view of government.
God calls all of his children to the table. We can disagree and even say a lot of hateful things, but what we can't do in good conscience is leave the table. Or demand that someone else not be at the table.