...and some are about the emotions that keep people from doing what they should--emotions such as hate for everyone in a certain category, or patriotism connected with historical falsehood. Those songs and poems (and paintings and and and...) can be a little dangerous to the people who like them, and to the people those people hate.

In other words, an artistically good but morally bad song deserves to be sung only if you don't let it change your mind. Which isn't that hard.