Since I've already chimed in, I guess I should offer my opinion on the larger subject.....
I can support marriage equality and same sex marriage. I understand the various biblical positions, but let's face it....everyone doesn't live according to the Bible and this country was founded on the premise that you don't have to. The law of the land does not have to be rooted in Scripture. So, for those who don't claim the Bible as their life's direction and are living a life that includes being in love with someone I certainly would not be in love with, that's their business.
I think I mentioned a lonnng time ago in a thread far far away that one of the most enduring and committed relationships I've witnessed is one of my colleagues and his life-partner of over 20 years. If they were allowed to get married, my life would not be detrimentally impacted at all and their lives would improve (health care and survivor benefits laws). So why should I get to say what they can do? If same sex marriage is not supported, they're not going to separate and find heterosexual relationships. They don't need to and quite frankly, it would be disastrous if they tried. Remember folks, we are not dealing with the ECUMENICAL definition of marriage here....only the LEGAL definition. Equal treatment UNDER THE LAW of a country that purports to have no favored religion.
As for the slippery slope into polygamy and incest, that is easily handled by the same set of laws that may or may not chose to allow gay marriage. Incest in particular has a foundational challenge in that there is a public health element to it due to the increased likelihood that children born to an in-breeding situation can be more susceptible to hereditary conditions that could then be passed on to their children. [insert HIV reference here] [insert reference to all STDs as counter-argument here]
I don't think it is an issue of the "traditional form" of marriage being "found unconstitutional". That is not and never was the question. Marriage as we know it today IS CONSTITUTIONAL and WITHOUT CHALLENGE. What is being challenged is the exclusion of same sex marriage. I have no problem with same sex marriage.