I think, too, there are different types of evil spirits.
I especially like your point that classes should be offered on this. In our world evil is common. News of genocide almost goes unnoticed. Immorality is even part of our churches. Acceptance of evil is just beginning to come to the field of psychology.
My friend and I discussed this for some time one afternoon. He felt we should only study Christ, that putting knowledge of evil in our minds wasn't profitable. I felt that knowing about evil and being able to recognize it, know how damaging it is, and how to avoid it was profitable. Both of us had valid points. Even in the Lord's Prayer, we pray to be delivered from evil. Evil is in our world, more powerful than ever. How can we stay away from it if we don't recognize it? Evil is promoted by teaching humanism, by teaching tolerance to mean acceptance of evil, by teaching that our possessions are a mark of our worth, that looking sexy is a good thing, that books, TV, movies need to be exciting with pictures of evil. Many ways. Shouldn't we learn to recognize it?