Genital cutting on children of both sexes, despite the scientific advances that have been made showing how the potential benefits do not outweigh the risks.
The distress caused to the children is abominable, and religious thinking lets parents somehow abdicate their responsibility for that suffering and refuse to protect their infants in the “hope there is more to this than I can see or understand.” Wonderful. You have no evidence that there was any point to the suffering, and absolutely no reason to think that there was any point. You just give up, let someone chop off a sensitive bit of anatomy and listen to the crying you could have stopped and hope. Well done.
The question doesn’t detract from it being one of the evils of religion, but makes me wonder what is the best way to stop it.
ALSO NOTE: I schedule these for the days I’m at work well in advance and, in the meantime, Ophelia Benson did a much better job than I could with this piece. Go read it.