The Heritage Foundation’s Ryan Anderson has an excellent paper exposing the folly of the widespread assertion that laws defining marriage as the union of man and woman are like laws banning interracial marriage:
Great thinkers throughout human history—and from every political community up until the year 2000—thought it reasonable to view marriage as the union of male and female, husband and wife, mother and father. Indeed, support for marriage as the union of man and woman has been a near human universal. The argument over redefining marriage to include same-sex relationships is one over the nature of marriage. Same-sex marriage is the result of revisionism in historical reasoning about marriage.
Bans on interracial marriage and Jim Crow laws, by contrast, were aspects of a much larger insidious movement that denied the fundamental equality and dignity of all human beings and forcibly segregated citizens. When these interracial marriage bans first arose in the American colonies, they were inconsistent not only with the common law inherited from England, but also with the customs of prior world history, which had not banned interracial marriage. These bans were based not on reason, but on prejudiced ideas about race that emerged in the modern period and that refused to regard all human beings as equal. This led to revisionist, unreasonable conclusions about marriage policy. Thinking that marriage has anything at all to do with race is unreasonable, and as a historical matter, few great thinkers ever suggested that it did.
The male-female nature of marriage is intrinsic to the perennial understanding of marriage:
Marriage is the institution that different cultures and societies across time and place developed to maximize the likelihood that a man would commit to a woman and that the two of them would then take responsibility for protecting, nurturing, and educating any children that they may create.
Far from having been devised as a pretext for excluding same-sex relationships—as some now charge—marriage as the union of husband and wife arose in many places over several centuries entirely independent of and well before any debates about same-sex relationships. Indeed, it arose in cultures that had no concept of sexual orientation and in some that fully accepted homoeroticism and even took it for granted.
By contrast, “Bans on interracial marriage had nothing to do with the nature of marriage and everything to do with denying dignity and equality before the law.”
Political grandstanding aside, I have to doubt that there are many people who genuinely believe that laws defining marriage as the union of man and woman are like laws banning interracial marriage. To anyone who purports to believe that, I would ask: Did you enthusiastically vote for Barack Obama in 2008 (when he maintained that he opposed redefining marriage)? If so, is it conceivable that you would enthusiastically vote for someone who said that he supports laws banning interracial marriage (even if you believed he didn’t really mean it)?