Thankfully we have freedom of speech so that those who want to read can choose their reading material for themselves - even if it is garbage- rather than leave it up to whomever has a match and too much political power.
No book is a threat if you raised your children properly; my folks never exercised any restraint on our reading material and none of us fell away. In the case of fantasy books all you need do if you really don’t trust how well you’ve taught your kids, is read the books with them and hold a conversation with them about the material. That way they know the hot topic of their peers without being consumed by it, and can in turn influence the unchurched readers in ways they otherwise could not.
True. Always read or be aware of what your kids are doing no matter how hard it is. Even then, stuff happens that you have no control over. Raising kids is hard! I’ve been fortunate. Even those parents who do everything they can, have kids who stray.