There are so many genres in film it's mind blowing.
I grew up on various film eras including black and white (horror), 50's alien horror/scifi, and horror in general.
It's not a bad genre. The same minds that gave us "The Texas Chainsaw Massacre" that was somewhat based off a real person also gave us "The Passion of the Christ". They can show us the minds of people who are for and against God. Who think their faith is strong when in reality it is weak; "The Exorcist".
I've spent many years in enjoying and learning about film.
God made us so special and unique on a level most don't understand. Even bad movies have a story to tell (Sharnknado 1-5).
IMO, one could watch an "evil" movie and still learn a lot from it. If Hollywood is even remotely right on exorcisms, the effect on the body, and how they are done then that should scary everyone.