There are earnest people who recommend realistic reading for everyone because, they say, it prepares us for real life, and who would, if they could, forbid fairy-tales for children and romances for adults because they ‘give a false picture of life’—in other words, deceive their readers.

I trust that what has already been said about egoistic castle-building [i.e. the reader lives vicariously as the hero of the story] forearms us against this error. Those who wish to be deceived always demand in what they read at least a superficial or apparent realism of content. To be sure, the show of such realism which deceives the mere castle-builder would not deceive a literary reader. If he is to be deceived, a much subtler and closer resemblance to real life will be required. But without some degree of realism in content—a degree proportional to the reader’s intelligence—no deception will occur at all. No one can deceive you unless he makes you think he is telling the truth. The unblushingly romantic has far less power to deceive than the apparently realistic. Admitted fantasy is precisely the kind of literature which never deceives at all. Children are not deceived by fairy-tales; they are often and gravely deceived by school-stories. Adults are not deceived by science fiction; they can be deceived by the stories in the women’s magazines. None of us are deceived by the Odyssey, the Kalevala, Beowulf, or Malory. the real danger lurks in sober-faced novels where all appears to be very probable but all is in fact contrived to put across some social or ethical or religious or anti-religious ‘comment on life’. For some at least of such comments must be false. To be sure, no novel will deceive the best type of reader. He never mistakes art either for life or for philosophy. He can enter, while he reads, into each author’s point of view without either accepting or rejecting it, suspending when necessary his disbelief and (what is harder) his belief.

C.S. Lewis, An Experiment in Criticism 67-8

The last part makes it clear that he does think some literature is dangerous; but it’s dangerous in ways different from how many people imagine.