I think a lot of it has to do with the black-and-white version of the world people are brought up in. Right and wrong. Good and evil. God and Satan. It's either all one or all the other. They don't learn about shades or gray when they're little, probably because their parents and teachers don't know much about it, and when they're confronted with it as adults, they get confused and annoyed and suspicious and reject it. I think that's why so many people fall prey to charlatans: believing in the absolutism of good and evil yields easy answers, and when charlatans merely cloak themselves in the trappings of what's considered good, simple people accept them without question.
I think America, as a society with a high percentage of its people steeped in judgmental religion, is more susceptible to his line of thinking than most countries, or at least most first-world countries. It's almost as though we're a first-world country with a third-world culture, and even people who aren't religious, or who reject religion, people who consider themselves educated and worldly, are affected by it, I think. It's mostly harmless, until the moment it's not.