Jonathan Rauch, a defender of same-sex marriage, explains why the comparison to racist laws that banned interracial marriage are not parallels to objections to SSM. From his article "Opposing Same-sex Marriage Doesn't Make You a Crypto-Racist":
By contrast, marriage has not always been racist. Quite the contrary. People have married across racial (and ethnic, tribal, and religious) lines for eons, often quite deliberately to cement familial or political alliances. Assuredly, racist norms have been imposed upon marriage in many times and places, but as an extraneous limitation. Everyone understood that people of different races could intermarry, in principle. Indeed, that was exactly why racists wanted to stop it, much as they wanted to stop the mixing of races in schools. In both intent and application, the anti-miscegenation laws were about race, not marriage.