"Really sick" is subjective, but harmful, dangerous, and exploitative certainly apply to much of the anal sex (and other anoreceptive activities) in porn -- and, sadly, outside of it as well.
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I would also add that many in that vocal segment probably are sadistic and/or sociopathic, and they've managed to make mutilation of an important--albeit highly undervalued and commonly maligned--body part mainstream and acceptable, when it should be neither of those. Worse still, plenty of people who wouldn't overlook, say, a woman's foot with missing toes or a gangrenous breast will ignore (if they're not jerking off to) a diseased and/or damaged anus, even when it's horrendously disgusting and/or the rectum slips out.