I decided to post here. I must admit being absent from the thread while this little back and forth went on so i'm not sure who's point I'll be helping here.
Quoting from the Supremes decision in Loving v. Virginia,
Marriage is one of the "basic civil rights of man," fundamental to our very existence and survival. (citing Skinner v. OklahomaTo deny this fundamental freedom on so unsupportable a basis as the racial classifications embodied in these statutes, classifications so directly subversive of the principle of equality at the heart of the Fourteenth Amendment, is surely to deprive all the State's citizens of liberty without due process of law. The Fourteenth Amendment requires that the freedom of choice to marry not be restricted by invidious racial discriminations. Under our Constitution, the freedom to marry, or not marry, a person of another race resides with the individual and cannot be infringed by the State.
The application of the 14th Amendment does not necessarily require race to be at issue (if that's what part of the argument was). Equal protection of the laws applies to all citizens (gays, of course, being citizens).
Where I think the difficulty lies is that in the Federal Law marriage has been defined as between a man and a woman. Thus, in the states where State Supreme Courts have interpreted their 14th amendment (look alikes in their state constitutions) to support gay marriage, that interpretation has not translated to provide Federal benefits like social security etc.
Further, if you look at the first sentence in the cited portion of Loving, the second part of that sentence does not apply in the gay context. Gay marriage is not fundamental to our existence and survival. Without this support, I'm not sure that the remainder of the Court's argument would be the same within the gay context.
I think because of the Federal Definition of marriage and the lack of underlying support from Loving, the court interpreting the 14th Amendment would be hard-pressed to find a "civil right" in gay marriage. It is clear they have found a civil right in hetero sexual marriage, but the underlying argument that makes it a civil right disappears when the gay issue is introduced because gays cannot reproduce which, clearly from the citation in both Skinner and Loving is very important to the court.