Morality of laws, Gay Marriage

I read a very good book about "Justice, what's the right thing to do" from Michael J. Sandel (all the citings are from there). A very good aspect from him is, that for every law a government defines, there is some moral background behind. The current state of the law(s) is reflecting the viewpoint of the society for the time being.
Michael Sandel comes up with the example of the gay marriage, and he's showing the following three alternatives how the state can be involved and define the allowed combinations and consequences:

"1. Recognize only marriages between a man and a woman.

2. Recognize same-sex and opposite-sex marriages.

3. Don’t recognize marriage of any kind, but leave this role to private associations."

Currently we are in some kind of a transition phase between option 1 and option 2, at least in Germany. If you have the opinion that this is a step forward in the evolution, you will also think how far behind other cultures like the Arab countries are.
The question is also which virtue a marriage is honoring:  
"If marriage is an honorific institution, what virtues does it honor? To ask that question is to ask about the purpose, or telos, of marriage as a social institution. Many opponents of same-sex marriage claim that the primary purpose of marriage is procreation. According to this argument, since same-sex couples are unable to procreate on their own, they don’t have a right to marry. They lack, so to speak, the relevant virtue."
Very interesting is also that just now the highest German court ruled that there must be no difference in supporting gay marriage as it is for non-gay marriage, as e.g. procreation is not mandatory for a non-gay couple.
Why not going for option 3, leaving the state out completely and let the people decide?
"“If marriage were an entirely private affair,” Kinsley reasons, “all the disputes over gay marriage would become irrelevant. Gay marriage would not have the official sanction of government, but neither would straight marriage.” Kinsley suggests that domestic partnership laws could deal with the financial, insurance, child support, and inheritance issues that arise when people co-habit and raise children together. He proposes, in effect, to replace all state-sanctioned marriages, gay and straight, with civil unions."

This sounds very similar to me to the separation of the church from the state not so long time ago (1919 in Germany).