The trouble with Martha Nussbaum’s analogy between revulsion at “taking the penis of one man and putting it in the rectum of another man and wriggling it around in excrement”, and discarded disgust-based policies, from India’s denigration of its “untouchables” to the Nazi view of Jews, to a legally sanctioned regime of separate swimming pools and water fountains in the Jim Crow South, is that only the first moral sentiment has a sound basis in physiology. Any sort of anal penetration is intrinsically harmful, even when it gets done by a proctologist, just as any sort of radiation exposure is harmful, even when it is administered for therapeutic or diagnostic purposes. The physical effects of anal penetration, precipitated by the concomitant trauma to the connecting tissue, are analogous to injecting raw sewage into the recipient’s bloodstream. Incontinence is another common and well-documented effect of receptive anal intercourse. By contrast, no health liabilities inhere in being a Jew or a Dalit, or mixing different races at a common water supply. If in doubt, consult your doctor.