You can look at evil things in art from two perspectives.
- You can see it as offensive and evil.
- You can see the truth that it tells.
When you see a painting with naked men and women as subjects, you could turn away and say it is pornographic and lustful. Lust is wrong. It is a sin.
Or you could use reason and critical thinking to determine the meaning of the painting, the truth it tells.
It is a mistake to judge a piece of art, like a painting, movie, or song, based only on what sins or visuals it portrays. We are better off to judge it based on what resulted from those sins as well. If the results were truthful, then why should we have a problem with it?
On the other hand, if the main character of a film kills ten random people in cold blood and doesn’t suffer any of the consequences that would almost certainly come to a murderer (prosecution, emotional anguish, remorse), only then might you consider the film (or whatever piece of art) as being evil or wrong.
Even then, the work may still be valuable in that it shows how a human can end up in such a circumstance (mental trauma, desperation) or how ridiculous the circumstance is.
When consuming or participating in art, the important thing is that we use reason in our judgement rather than taking the extreme and/or lazy routes of totally accepting a piece of art no matter its value or totally rejecting a piece of art based purely on its surface value. By taking a puritanical view on art, we are certain to miss out on many valuable lessons. Even if there are no lessons, if the creation is completely futile, at least we can practice the virtue of empathy by attempting to understand the feelings of the artist.