Fairy tales don't need to tell children that dragons exist; children already know that dragons exist. Fairy tales exist to tell children that dragons can be killed.
- G.K. Chesterton
This reminds me of my favorite scene from Aliens in which Ripley discusses the existence of monsters with Newt, a child who'd been hiding in a facility overrun with the acid-blooded alien creatures ...
NEWT: My mommy always said there were no monsters. No real ones. But there are.
Ripley's expression becomes sober. She brushes damp hair back from the child's pale forehead.
RIPLEY:(quietly) Yes, there are, aren't there?
NEWT: Why do they tell little kids that?
Newt's voice reveals her deep sense of betrayal. She's seen that the world can be just as terrifying as her most primal child's nightmare if not more so, and that's a lot worse than finding out there is no Santa.
RIPLEY: Well, some kids can't handle it like you can.
Monsters exist. But monsters can be killed.