Some more sharp observations from John Corvino's book What’s Wrong with Homosexuality? (NY: Oxford UP, 2013)--these from his chapter on natural-law arguments against homosexuality: as Corvino notes, the term "unnatural" is frequently used in an exceptionally loose way as a rhetorical tag for all sorts of practices and behaviors to which one objects. The very looseness of the term as it's usually applied is part of its rhetorical power, as the term evokes a visceral reaction of repulsion its users hope to evoke, while also precluding the kind of careful thought that might make people think twice about the easy tagging of something as "unnatural":
The looseness of the term "unnatural" may be part of its rhetorical appeal: it can be tossed around to evoke disgust, without much worry about consistency. . . . At times, "unnatural" appears to be nothing more than a rhetorical flourish, invoked to smear things that the speaker finds abhorrent” (79).
Corvino also notes the curious fact that most people who condemn homosexuality as unnatural completely ignore the fact that Christian natural-law theory has long condemned masturbation as unnatural, too--a position that proponents of what's being called "new natural law" (NNL) are trying to revive:
It is worth adding that any view that rests the wrongness of homosexual conduct on the wrongness of masturbation ought to face a severe burden of persuasion. The fact that many people approvingly cite natural law theory to condemn homosexuality while ignoring its other conclusions says a great deal about people’s capacity to tolerate inconsistency in the service of prejudice (96).
For the rest of us, it often seems that an act is unnatural when the person making the claim finds it abhorrent or revolting. Thus homosexuality, but not masturbation; eating dog meat, but not eating pork; interracial relations generally, but not John Rolfe and Pocahontas. (Prior to being struck down in 1967, Virginia anti-miscegenation law defined anyone with "one-sixteenth or less of the blood of the American Indian" as white, in order "to recognize as an integral and honored part of the white race the descendants of John Rolfe and Pocahontas.") "Unnatural" according to this view is simply a term of abuse, a fancy word for "disgusting," a way to mark visceral reaction as well-considered moral judgments. We can do better (97, citing Loving v. Virginia 388 U.S. 1 , fn. 4).
Many contemporary Christians who slur those who are gay as unnatural would be very surprised to discover, I suspect, that the great Catholic theologian Thomas Aquinas regarded masturbation (and oral sex) as gravely offensive to God because these are unnatural acts more seriously sinful than the rape of a woman by a man, which at least has the potential to result in conception. As the Catechism of the Catholic Church notes unambiguously (¶ 2352), masturbation has "in the course of a constant [Catholic magisterial] tradition" been regarded as an "intrinsically and gravely disordered action."*
Yet this is a constant teaching that seems to be almost nowhere on the radar screen of many Christians today for whom homosexual acts are uniquely and in an exemplary way unnatural, though advocates of NNL are now trying to revive the idea that masturbation and oral sex--any kind of genital sexual activity at all that results in orgasm, in which the penis is not inserted into the vagina--are always and everywhere intrinsically disordered, gravely sinful, unnatural acts.
* ¶ 2352 goes on to say that "the moral sense of the faithful" has never been in any doubt, and has consistently and firmly maintained. that masturbation is an intrinsically and gravely disordered action. I wonder what empirical evidence backs up this catechetical claim about "the moral sense of the faithful" and what it has consistently held and firmly maintained without any doubt at all.