This information comes from website “Catholic Answers”.  Information sources are cited at the end of this document and are noted in blue font.

“Marriage, is a major public health issue and not just a private affair. Marriages that are exclusive, permanent, unconditional, and life-giving contribute much to public health and longevity; marriages that fail any of these criteria and end in divorce create an enormous social, emotional, and health care burden for the couple, their children, and society.”

INFEDELITY, PROMISCUITY AND INSECURITY WITHIN HOMOSEXUAL RELATIONSHIPS

• One study in San Francisco showed that 43 percent of male homosexuals had had more than 500 sexual partners.55 Seventy-nine percent of their sexual partners were strangers. Only 3 percent had had fewer than ten sexual partners.56

• Lesbians are less promiscuous than male homosexuals but more promiscuous than heterosexual women: One large study found that 42 percent of lesbians had more than ten sexual partners.57 A substantial percentage of them were strangers.

• The statistics speak for themselves: If homosexuals of either gender are finding satisfaction, why the search for sex with a disproportionately high number of strangers? In view of the evidence, homosexuals will not succeed at establishing exclusive relationships. Promiscuity is a hard habit for anyone to break, straight or homosexual. Promiscuous heterosexuals often fail to learn fidelity; male homosexuals are far more promiscuous than heterosexual males, and therefore far more likely to fail. Lesbians are more promiscuous than heterosexual women. There is little good data on the stability of lesbian relationships, but it is reasonable to speculate that their higher rates of promiscuity and various deep-seated psychological problems would predispose them to long-term relational instability. Existing evidence supports this speculation.58

• The more radical homosexual activists flaunt their promiscuity, using it as a weapon against what they call "bourgeois respectability."59 But even more conservative advocates of gay marriage such as New Republic editor Andrew Sullivan admit that for them, "fidelity" does not mean complete monogamy, but just somewhat restrained promiscuity.60 In other words, they admit that exclusiveness will not happen. And without exclusiveness, their "marriages" will have little meaning.

Sullivan argues that marriage civilizes men, but anthropology would counter that marriage to women civilizes men. Male humans, homosexual or heterosexual, are more interested in random sex with strangers than women are.61 Men need to be civilized, to be taught the joys of committed sex, and that lesson is taught by marriage to women, not by other men who need to learn it themselves. The apparent instability of lesbian relationships suggests that lesbians understand that lesson less well than heterosexual women do. Exclusivity will not happen, and without exclusivity, marriage does not exist.

Without exclusivity, permanent and unconditional relationships will not happen, either. By definition, a relationship that allows for "cruising" will be shallow and mutually exploitative, just as sex with strangers is shallow and mutually exploitative. So far, same-sex marriage is 0 for 3: likely to be neither exclusive nor unconditional nor permanent.

Footnotes:
55. A. P. Bell and M. S. Weinberg, Homosexualities: A Study of Diversity Among Men and Women (New York: Simon and Schuster, 1978).
56. Ibid.
57. Ibid.
58. S. Sarantakos, "Same-Sex Couples: Problems and Prospects," Journal of Family Studies 2 (1996): 147-63; P. Tjaden, N. Thoennes, and C. J. Allison, "Comparing Violence Over the Life Span in Samples of Same-Sex and Opposite-Sex Cohabitants," Violence and Victims 14 (1999): 413-25.
59. Stanley Kurtz, "What Is Wrong with Gay Marriage," Commentary, September 2000, 35-41.
60. Andrew Sullivan, Virtually Normal: An Argument About Homosexuality (New York: Alfred Knopf, 1995).
61. D. M. Buss, The Evolution of Desire: Strategies of Human Mating (New York: Basic Books, 1994); D. Symons, The Evolution of Sexuality (New York: Oxford University Press, 1979); M. Ridley, The Red Queen: Sex and the Evolution of Human Nature (New York: Penguin, 1993); S. Goldberg, Why Men Rule: A Theory of Male Dominance (Chicago: Open Court, 1993).