The warning need not apply to any rational person.
All fiction is Goldie Locks. It's pure nonsense.
Your comment is (forgive me) the kind of useless observation which invites tautological formulation:
"Rational people aren't influenced by fiction."
"Such-and-such educated, intellectually sophisticated, accomplished persons were much influenced by works of fiction."
"Ah. Then they couldn't have been truly rational."
(Alternatively: "Ah. Then it couldn't have been truly fiction.")
Your assertion is immune to any countervailing evidence or disproof because its conclusion is really just an aspect of its own definitions.