Same sex marriage advocates are not advocating government disengagement from marriage. In fact, by pursuing their cause with the arguments thus far advanced, they are validating government engagement in marriage.
My personal preference is that government stay the hell out of marriage. That view appears to command an even smaller minority than advocacy of same sex marriage.
As a purely strategic consideration, if one wishes to win support for same sex marriage, championing same sex marriage as a way to bolster family units and stable home environments for children is a solid approach; as Redress has pointed out, there are a sizable number of same sex couples who wish to adopt, and who could provide good homes to members of the next generation--something there is a decided scarcity of at the moment. No, same sex couples do not have much procreative potential; they do have parenting potential, and adopting potential, and there are certainly enough children in need of adoption by good parents to give the argument substance.
Tactically, the family unit argument leaves social conservatives with few substantive responses:
- Rebut on the basis that same sex couples are unfit as parents.
- Withdraw marital regulation from the State's police power, and endorse civil unions to manage the legal aspects while preserving the religious sacrament of marriage.
- Endorse same sex marriage.
Option #1 is a guaranteed loser, for the simple reason that the opposite has already been proven to be true: same sex couples are quite capable of being fit parents. Social conservatives would lose credibility, and the debate, and same sex marriage would carry the day.
Option #2 is a compromise that would let everyone declare victory.
Option #3 is basically surrender.
To echo Jerry's question: Why not make a winning argument? Why all the bobbing and weaving to avoid making that winning argument?