We use the word “evil” when we want to stop thinking about the roots of unacceptable behavior.
Look at how often the word “evil” is preceded by the words “just plain,” as in “Them Moozlim ter’rists is just plain evil, is all it is.”
This use runs across lines of party and principle, and it serves to literally demonize the other side. Liberals label giant corporations evil, and conservatives have used the term on Hillary Clinton.
As recently as 50 years ago, the subject of evil was up for philosophical debate. Today, we don’t try to understand it at all.