I'm generally inclined to agree with this. Science fiction was always my first love, but I used to be quite fond of high fantasy, and even as a small child it never occurred to me that it was representative of the real world. Later on I would often have a great deal of fun trying to invent scientific models to explain the unusual physical behaviours of these alternate universes. Good fantasy settings generally do not disagree with the scientific method, just the particular environment in which that method is applied.

That said, there does exist a number of children that actually believe in the existence of certain fantasy universes. But in my opinion that is no more reflective of the genre itself than 'quantum healing' is of quantum mechanics. Children should be taught general skepticism, but that does not preclude interactions with far-fetched fiction (indeed, it is often useful to have a standard by which to judge the patently false!).