Quæ dolent ea molestum est contingere.

You touched him in a tender part, and brought to his memory some instance of vice or folly he would gladly have forgotten. This, however, is equally a breach of good manners, as it would be of humanity to tread on the foot of a person afflicted with corns or the gout, or to handle rudely any part that was diseased or wounded: No se ha de mentar la soga, en casa del ahorcado, we should not mention a halter in the house of one whose father was hanged.