A major basis for "queer" studies is the de-essentialization of human nature, or the denaturing of nature. Once the entire Aristotelian-Thomistic metaphysic is scrapped, typically in favor of "de-ontic" existentialism, the concept of "essence" disappears too. And without "essences", or pure, objective modes of being, there is no essential human nature. Human nature is, instead, a plastic historical and biological construct. Since there is no "human nature," but only persons behaving under the banner of humanity, homosexuality cannot be a violation of human nature. Once the concept of real, essential nature disappears, natural law (as an expression of absolute truth embedded in human consciousness) loses its standing in the public much less private square.
The problem for me is that precisely by de-absolutizing human nature, queerists (if I may) as a rule, of not indeed as a necessity, absolutize queer nature. The reigning argument of the past couple decades in defense of homosexuality is basically that it is a legitimate, indeed naturally legitimate, expression of human sexuality. But by claiming a natural basis for queerness, queerists just swap saddles and continue riding the same essentialist horse. By arguing for autonomous queer studies, queerists just reinforce the older essentialist paradigm. By claiming homosexuality is authentically human, queerists imply something really is authentically human. Their critical metaphysical (existentialist) method undermines their own ideological goals.
If queerists however take the more radical, denatured line of thought, they eo ipso renege on rights to claiming "queer" is (also) "authentically human," since on radical existentialist lines nothing is authentically, essentially human. The problem, the risk of radical queerism, is that once queerism disqualifies itself from the realm of the "truly human," it opens itself to the danger of an absolutizing fascism in its opposition. "You say you are not 'essentially human'," asks the queer's opponent, "because nothing is essentially anything? Very well, then. We will simply take up the gauntlet and vanquish you, our non-human opponents, without the milk of human kindness."
The basic (and I believe lethal) flaw in queerism is that by legitimizing homosexuality on the grounds of human dignity and autonomy ( i.e., "I'm a human too, so you must respect my way of being human!"), it eo ipso posits an essential anthropological substratum (of what should be universally protected human nature). This essential human substratum -- let's call it "essential anthro-autonomy " -- in turn destroys the ethical "space" created for homosexuality on the grounds that it's not "against human nature," since there is no human nature! But the question stands: Which is it? An essentially queer human nature, rooted in an unwittingly essentialist ontology? Or a radically existential monad rooted in personal autonomy? As long as queerism insists it is an essentially human category of being and thought, it never owns up to its most basic existential, anti-essentialist commitments. How queer indeed.