Fairy tales do not tell children the dragons exist. Children already know that dragons exist. Fairy tales tell children the dragons can be killed.
-G. K. Chesterton
A related quote that I also like:
Since it is so likely that children will meet cruel enemies, let them at least have heard of brave knights and heroic courage. Otherwise, you are making their destiny not brighter, but darker.
Monsters are real.
We tell children monster stories, not to tell them that monsters exist, but to tell them that the monsters they already know can be defeated.
-G. K. Chesterton
A related quote that I also like:
-C. S. Lewis