I'm not sure it's a huge jump; I think honey's pointing out that you don't have to believe in something to be interested in it, so not believing in exorcisms doesn't really tell us why you're not interested in the The Exorcist.
However, there are elements that often turn me off--one being scenes designed to shock or outrage me, whether it's the Alien bursting out of someone's belly or Jaws nipping at victims or Linda Blair's revolving head spraying green soup. Don't care much about the smoke and mirrors depiction of demonic possession, yet I liked the storyline and the director's original desire not to show the demon in the Dana Andrews classic Night of the Demon. I'm also not much on parables about Catholic doctrine, whether it's The Exorcist, The Da Vinci Code, or Shoes of the Fisherman. On the other hand, give me Orson Welles as the Borgia pope in The Prince of Foxes, and that I understand. Monty Python and the Holy Grail, fine; The Da Vinci Code, no.
Although not an element in The Exorcist, I'm generally repulsed by anything that takes the so-called Burmuda Triangle serious, especially the alleged "missing formation." So when in Close Encounters those dufus scientists turn a corner 10 minutes into the movie and come face to face with 5 Avenger dive bombers, I was ready to run for the exit. If I only had, I wouldn't have been subjected to Dreyfus bringing dirt and bricks inside to build a scale model of the Devil's Tower instead of using an extension cord to put the TV on the back porch and build his model mountain in the yard. Never did figure out why the aliens were sending message to the only guy in the US who didn't recognize the Devil's Tower national landmark.
Bottom line: I like good fiction. But there are some subjects and a few actors who I'd rather just avoid. I liked The Day the Earth Stood Still, a flying saucer film for intelligent adults. I didn't like the childish E.T.