it’s this idea that awful/morally disgusting people also must be ugly, unappealing, unskilled, anything undesirable or considered negative by social acceptability norms. and by extension to maintain your "goodness" you must suddenly see all their work as terrible, them as ugly, +
The Neil Gaiman example later in this thread is absolutely evergreen because he's such a perfect case study for "terrible people can make very good and very progressive, empathetic pieces of art". The sooner we stop conflating someone's morality with their work the better.
Keep in mind that the Egyptians were doing shit like this way back in 2500 BC so the precedent for super realistic anatomy was already well established for nearby Bronze Age cultures like the Minoans