Perhaps Nigerian scammers? Nowadays everyone knows that Nigerian scammers are likely going to take you for a ride, and what tactics they use. And how much it hurts to get stung by one.

You could use the idea of benevolent Nigerian Princes as the 'known false' idea that everyone can agree on, and segue into the features of it that ring alarm bells (high payoff for sending personal info, undeserved wealth triggering our 'greed' buttons, etc) and the idea that being primed on rationality helps you to not fall for whatever the next version of Nigerian scamming turns out to be.