You can brainwash the majority of people, it doesn't mean they're all stupid. It used to be that the priests/vicars would be some of the smartest people as they could remember all the rules, these days Big Pharma is the modern day religion, now it is the doctors who are good at memorizing the teachings of Church of Big Pharma, the majority of people are in this religion without even realizing that that's what it is. They're not all stupid, the brainwashing can be very convincing