People's deepest moral beliefs and values are modified by the fiction they consume. For example, fictional portrayals of members of different races affect how we view out-groups. After white viewers see a positive portrayal of black family life - say, in The Cosby Show - they usually exhibit more positive attitudes toward black people generally. The opposite occurs after white people watch hard-core rap videos. What is going on here? Why are we putty in a storyteller’s hands?
One possibility, to borrow the words of Somerset Maugham, is that fiction writers mix the powder of a message with the sugary jam of storytelling. People bolt down the sweet jam of storytelling and don't even notice the undertaste of the medicine (whatever message the writer is communicating). A related explanation comes from the psychologists Melanie Green and Timothy Brock. They argue that entering fictional worlds "radically alters the way information is processed." Green and Brock's research shows that the more absorbed readers are in a story, the more the story changes them. Fiction readers who reported a high level of absorption tended to have their beliefs changed in a more "story-consistent" way than those who were less absorbed. Highly absorbed readers also detected significantly fewer "false notes" in stories - inaccuracies, infelicities - than less transported readers. Importantly, it is not just that highly absorbed readers detected the false notes and didn't care about them (as when we watch a pleasurably idiotic action film); these readers were unable to detect the false notes in the first place.
Gottschall, Jonathan. The Storytelling Animal: How Stories Make Us Human (p. 151). Houghton Mifflin Harcourt. Kindle Edition.