The definition of marriage as being between a man and a woman is not the result of bigotry; it’s the result of the unchangeable facts of biology. Marriage existed before government (and certainly before government attempted to define it). It’s the natural result of the fact that the man/woman union produces children, and it exists to bind the man, woman, and child together for the stable good of everyone in society.
As Trevin Wax explains, nature itself discriminates against same-sex marriage:
Traditional marriage celebrates the bringing together of the two halves of humanity, the sexual union of a male and female that bears fruit in new life. Nature is terribly discriminatory, for only traditional marriages bring forth children. That’s why, when a male-female couple is unable to conceive, we sense the loss and mourn. Deep down, we know that marriage is oriented (not exclusively, but profoundly) toward procreation.
Same-sex marriages, on the other hand, can only serve as the basis of a family that has been engineered. Children do not flow naturally from the marriage. The relationship can be loving, stable, and committed, but the union is sterile, not artificially through birth control or tragically through infertility, but due to the nature of the union itself. Human bodies were designed to reproduce through the union of male and female. No other arrangement works. So, no matter how many times Macklemore sings “Same Love,” there is and will remain a profound difference in same-sex marriage versus traditional marriage. Only one kind of union can result in children.
It may seem like it’s useless to discuss lost political battles, but it’s still as necessary as ever for Christians to understand why we hold to a man/woman-only definition of marriage (see here for a theological reason, as well). Our understanding of the body, sexuality, and marriage will continue to be relevant, regardless of the law, not only because we will need to argue for our freedom to hold to this position in the future, but also because we must keep knowledge of this truth alive until our culture’s view of sexuality falls apart. And it will fall apart eventually. A false view of sexuality can’t be propped up forever because the consequences can’t be swept under the rug forever (for more on this, read Jeremy Neill’s argument that “On Human Sexuality, Conservative Victory is Inevitable”).
For more on the arguments for man/woman-only marriage, see “Understand the Same-Sex Marriage Issue.”