Tell their parents they're bad people for lying to their children and are probably the reason why so many people are going through an epistemological crises right now without realising
1. "It's like a bedtime story, but longer."
2. "it's to prepare you for government lies."
3. Break into their house dressed as Santa. Give them bad gifts and make them cry. Their parents will tell them Santa isn't real to make them feel better and it will be a good thing.