This danger is hardly confined to fiction. Even a completely true set of facts can be presented in multiple ways to support different agendas. Also--who takes the time to check every fact in every book they read? Quite a lot is taken on trust when reading nonfiction.

Anyway, this is only a danger if the reader is credulous about what they are reading. But reading a lot of fiction can help a person learn to detect an author's point of view, biases, and, in some cases, hidden agendas.

This learning can be greatly accelerated by training. College-level literature courses teach students the mental framework to critically evaluate any piece of writing.