The way I read it, he didn’t say everyone was that stupid. He just referred to “the idiot public” which doesn’t include everyone.
I’ve heard some actors talk about having been upset, usually when a director doesn’t tell them something is going to happen, in order to get a more natural horror reaction from them. (e.g. in Alien)
But I doubt the effect lasts very long for most of them.
As someone who’s played and written a lot of game scenes with violent and horror-worthy content, I would say for me that the reverse is pretty true. It’s a game, and thinking about such subjects tends to erode the horror effect that people have who don’t think about them or experience them regularly. Especially in one’s own work.