Why should Christians stay away from movies and books like Harry Potter?

Whenever characters in a novel or movie are given magical powers, whether it is the hero or another character, the power to see the future, a secret stone or chant that gives power, you are playing with the devil. If your impressionable children read that kind of thing, the Bible starts to seem less interesting than watching spells being cast, and worse, you are opening a porthole for the devil to come into the child's life. Demonic possession is real and is right beneath the surface; some of the possessed you can spot, others seem perfectly normal. So when you scratch in the wrong place, like reading Harry Potter, do not be surprised if something comes through; it may not be today or tomorrow, but watch out.