Good point. And then it will allow for the union of a man and a dog, a man and three small children, a women and four goats, ten men and forty two lemurs, two children and their pit bull, and...
Really, we care. Every state, apart from what it might be argued theoretically, has always relied upon some kind of world view system of morality. Whether that was the pagan view of Rome, or in the case of the US, in the biblical view of Judeo-Christian propriety.
We cannot escape such a connection between the underlying world view and the public morality, so the question will be: With what do we replace this with now?
The best we can do is be Salt of the Earth and hope people listen to us.