Great article. I didn't find The Exorcist that scary, but you may have indirectly explained why. Even when I look at my friends who find it super scary, they tend to be the more religious ones. The movie has a religious message and theme, and maybe that needs to resonate with the viewer because the film's scariness is based on the viewer's beliefs. It is a very culture specific film, I think (not good or bad, just an observation).