Where is the convincing evidence that homosexual unions contribute to the social interest in procreation comparable to the traditional male-female marriages?
Legalizing Same-Sex Marriage Would Undermine the Social Interests in Responsible Procreation and the Institution That Has Best Protected Those Interests
The most fundamental difference between heterosexual unions and same-sex unions with regard to procreation is that most heterosexual couples can for many years procreate as a couple (unless age, illness, infirmity, or intervention has deprived one or both parties of fertility), but no same-sex couple can ever procreate.
Legalizing same-sex marriage would weaken the nexus between procreation and parenting.
The confusion of social roles linked with marriage and parenting would be tremendous, and the message of "anything goes" in the way of sexual behavior, procreation, and parenthood would wreak its greatest havoc among groups of vulnerable individuals who most need the encouragement of bright line laws and clear social mores concerning procreative responsibility.
Advocates of same-sex marriage respond to assertion of society's marital interests in responsible procreation by citing six facts of life which allegedly undermine them: (1) marital infertility; (2) extramarital procreation; (3) use of assisted reproduction technologies by same-sex couples; (4) child rearing by same-sex couples; (5) overpopulation; and (6) modern expectations about marriage and child rearing.
First, it has been asserted that the present marriage law is underinclusive with respect to the procreation justification; the failure of the state to screen heterosexual couples who marry for their ability or willingness to procreate and the granting of marriage licenses to elderly couples (in their post procreative years) allegedly shows that procreation is not really a legitimate justification for traditional marriage laws.(92) However, this response mischaracterizes the nature of the social interest in procreation.
Allowing heterosexual couples to marry who physically cannot procreate because of age or infertility, or who have chosen not to procreate, while disallowing same-sex couples to marry makes substantial sense from the perspective of the state's interest in procreation, for several reasons.
Second, same-sex marriage advocates sometimes assert that since procreation can and does occur outside of marriage, this shows that the state's interest in procreation is hardly a prime purpose of marriage.(96) The fact that many children in America are born out of wedlock is undeniable.
Third, proponents of same-sex marriage sometimes argue that the procreation justification for male-female marriage is underinclusive because gay and lesbian individuals can and do procreate, either by sexual intercourse with someone of the opposite sex, or by means of artificial reproductive technologies.(99) This is undoubtedly true, but it misses the point.
Rather, the incentives of marital status should be used to encourage commitment of both mother and father to procreation and childrearing.(105) Moreover, legalizing same-sex marriage would not strengthen in any way the social interest in procreation or preservation of the link between procreation and child rearing because same-sex couples cannot procreate.
Fifth, some advocates of same-sex marriage deny that the "survival" procreation argument is still a valid social interest, arguing that the threat of overpopulation has made this argument obsolete.(106) Of course, the social interest in procreation is much more complex than gay rights advocates' reductio ad absurdum caricature.(107) The public interest in procreation for survival does not mean procreation for maximum population at subsistence level; the social interest is in responsible procreation.