[nickjr]

This could go under the broader "misconception" category :P There are a ton of non-debatable misconceptions floating around the world for various reasons, most of them communication-based (language barriers, misunderstandings, poor wording, the "telephone" game (or whatever it's called) effect, cognitive biases). Some of them finally poof as time goes on, but many persist. And mothers are usually very protective of their children, so they're gonna be extra cautious. It's definitely understandable if the mom is a typical mom in the sense that she really loves her kids.

I really hope I don't need to pull up examples of the many non-debatable common misconceptions ;P