I think the main reason is that most newer horror movies are rated "R" and TBM's aren't allowed to see movies above PG-13. Even then, some PG-13 movies are considered borderline if they're not part of the Disney Empire (Star Wars, Marvel, etc.)
what I absolutely adore about them - and others like them - is knowing that the monsters and scary things have to stay in the theater. They can't follow you home.
It's the same way with scary books. Once you close them, the monsters have to stay inside. That's the rule. They can't come out and get you.
Growing up, my TBM mother hated horror or anything not focused on happy characters having happy endings (ala Disney). I think most TBMs want to avoid anything "dark" and instead want to watch movies that bring on the warm-fuzzies.
I remember being 4 years old and watching Poltergeist with my parents. I think you all can guess where a lot of my parasomnias started, especially since there was a gigantic, ancient tree that tapped on my window during breezy nights.
Maybe it's the movies that bring a dark feeling or whatever the cult wants to call it and that's why they're supposed to be avoided? I remember the cult always telling people to avoid bringing in the dark/evil feelings.
I do enjoy horror movies now although torture porn films make me queasy. There are also some I will never watch like Salo, Human Centipede series, Cannibal Holocaust, and probably even Antichrist (despite having Willam Dafoe as a star) after reading about the worst scenes.
I remember when " The lost boys" came out. A lot of guys in my single young adults were talking negatively about it. It was one of my favourite movies at the time, so I had to keep quiet. I hate horror movies, but to me that one doesn't qualify. I also loved " The shining" when it came out.