Even if we accept the basic logic of the natural law argument against homosexuality, we have to ask just how wicked a sin it could really be. People sometimes use metal coat hangers as impromptu TV aerials, a purpose for which they were not designed. Likewise, children sometimes climb up slides instead of sliding down them. Are these activities heinous infractions of the moral law? Are they an insult to the people who designed the coat hangers or the slides?
(p. 247) - Darwin, God and the Meaning of Life: How Evolutionary Theory Undermines Everything You Think You Know (2010)