The legalities of marriage reinforce a traditional institution which is a cornerstone of civilization. We have not evolved beyond the need to have civilization-bearing institituions. To survive, they need to be important and held in esteem by a plurality of people.
As far as people cohabiting in the sexual relationship of their choice, I am in agreement: that is their business.
For the strength of the family in our nation, though, and for the continued health of traditional values, we should encourage one-man, one-woman marriages. It goes without saying that if we should encourage this existing traditional institution, it is a good idea for state governments to continue to take their accustomed role in doing so.
Nope. This is a societal issue, not a state issue. Failure to draw distinctions between the two makes you, by definition, a totalitarian.