I used to think the same thing. Be sure to Freepmail me if you change your mind about the topic in this life. Seeing one in person could immediately change your opinion about this and a number of other related areas.
Reading books by, and about, Exorcists confirmed my belief in the demonic. I recently met Father Gary Thomas who was the subject of the book “The Rite.” He was skeptical too until he attended exorcist training and participated in a few exorcisms. I highly recommend the book, the movie though, with Anthony Hopkins, was greatly sensationalized and only vaguely resembled the book.
Anyone who says that demons do not exist is simply not well informed.