What do you think about a movie involving a demented cult leader who orders his followers to kill rich and famous people in Hollywood?

lol Sounds like just the way Manson got his followers to do atrocious shit for him. Susan Atkins even wrote a book saying that that was exactly how Manson used to get 'em to do things - Always strongly hinting or suggesting something, but never directly ordering it.

Exactly what the former president of South Korea used to "force" loyal underlings to do assasinations, as depicted in the movie The Man Standing Next (2020.)

They would because it's all fiction.

And Hollywood doesn't care about the risk of giving the "crazies" any ideas, if they did then a large majority of the movies they've released would have never seen the light of day. There's already been a million ideas put out that could have potentially motivated some psycho into doing something, but didn't.