Brainwashing isn’t a secretive event that takes place in hidden rooms. No hypnotists or vials full of chemicals are required. It takes place every day on a massive scale across the United States.
Unlike Raymond Shaw in The Manchurian Candidate, brainwashing does not turn people into hypnotized zombies who would be ready to kill a presidential candidate at a command. Instead, it transforms them into the sort of people who would be willing to kill someone for political reasons.