Many who support the traditional male-female definition of marriage see homosexual marriage as an assault on a sacred institution. But in truth, that assault began long before the current gay marriage debate came to the fore. I have many times argued in favor of heterosexual marriage on the basis of marriage's dual purposes: (1) procreation and (2) the mutual love and support of the spouses. These two elements must be present for any marriage to be valid. At one time this truth was universally accepted throughout Western Civilization. But early in the Twentieth Century mainline Christian groups began chipping away at the foundations of traditional marriage.
As Genevieve S. Kineke explains in a recent post at Catholic Exchange:
"The Catholic Catechism says: “The matrimonial covenant, by which a man and a woman establish between themselves a partnership of the whole of life, is by its nature ordered toward the good of the spouses and the procreation and education of offspring” (CCC, 1601). Or to put it more succinctly: marriage is a gift of God, given for the sake of babies and bonding.
"The reason that such a foundational understanding of marriage has been called into question at this point in time is because our culture has cut marriage adrift from those two guiding principles. Decades back, the western world embraced the contraceptive mentality that separated the marital embrace from its natural fertility. The Protestant churches officially signed off on this fact as early as 1930 at the Lambeth Conference, eventually leaving the Catholic Church as the only religious body to stand firmly against contraception within marriage...
"The other part of marriage—the lifelong bond—has also lost society’s censure, as the next generation incorporated the newer attitudes towards intimacy. Premarital sex and declining sexual fidelity led to more divorces, which gradually became easier to obtain. Whereas previously those who chose to end their unions faced a subtle form of shunning by the larger community, such attitudes are entirely foreign to us today. Long gone is widespread denigration of promiscuity, cohabitation, out-of-wedlock births, divorce or serial monogamy, and each has subsequently risen to shocking heights."
Certainly we should defend traditional marriage against every attempt to destroy it. But there are many on our side of the debate who fail to understand the damage that has already been done from within. Many of those who actively support traditional male-female marriage do not themselves practice a marriage that is open to life, and all too often sex and intimacy are robbed of their sacredness.
We should certainly keep a united front against the homosexual assault on marriage, but we as Catholics bear a special responsibility to remind others what it is for which we fight.