In respect to a man’s sexual powers, which are unitive and generative by nature, the one whose state is best would be a man as husband and father, just as for a woman it would be as wife and mother. This is how we know that homosexual inclinations are privations and that homosexual acts are disorders. It is not a matter of “who says.” Homosexual behavior cannot actualize sexual potential because homosexual acts can be neither unitive nor procreative. Like a withered limb, congenital deafness, blindness, or a genetic predisposition to alcoholism, homosexual inclinations are not part of what a human being is in his essence. These are accidental, not essential properties. In each case, there is something missing that out to be there. For instance, the limb ought to be able to move in its full strength, the ear ought to be able to hear, and the eye to see. The further a thing is from its perfection, the more defective or “corrupt” it is—just as blindness is the furthest defect of the eye. A privation of the good cannot itself be good. In fact, as St. Augustine said, evil is a privation of the good.
Robert R. Reilly, “The New Gnosticism of the Homosexual Movement,” The Catholic World Report.