A quote from Sam Goldwyn: "Pictures are for entertainment, messages should be delivered by Western Union." Needless to say, the same goes for all forms of fiction, be it written on paper or celluloid.
Movies are inherently manipulative, since the filmmaker is basically showing you images that will make you feel a certain way...but novels leave a lot more up to the reader. Some would say that the success of Ayn Rand's books means that people are willing to be "instructed" by writers of fiction, but I think most of us probably read The Fountainhead for the story, and skimmed over all the pages of the author's speechifying.
I agree with Sol Stein, who said somewhere in his great book, Stein on Writing that we should never forget we are in the entertainment business. If people stop reading your writing--for whatever reason--you've failed on some level. Check out Sol Stein's website--lots of excellent quotes and excerpts.
I read C.S. Lewis' wonderful "Narnia" books as a child and never got any of the Christian symbolism, nor was I converted to his religious views, since I had no conception of a deeper meaning--and virtually no religious background; I simply enjoyed the stories as most children did--for the story. (Some actual bible stories might be enjoyed as literature--for those who haven't read much literature, and certainly the musical Godspell, with a book taken almost word-for-word from the Gospels, is great entertainment if done right. Here's a link to a short clip from the 70s movie version, with Victor Garber.)
Documentaries are another story, and it's unusual to see a doc without a message. Though their style of "arguing their case" may be subtle or obvious, the filmmaker's point of view should be clear. This short documentary film is a case in point. "Early Message/Primeros Mensajes", directed by Lizet Benrey and produced my Media Arts San Diego, and not shown the other night at the Latino Film Festival due to a technical glitch, is a good case in point. It's about the early childhood "lessons" we learn in bigotry, and about the work of the Anti-Defamation League. (Reminded me of the song from "South Pacific" "You've got to be Carefully Taught").
The Film Festival continues apace through the weekend, and we've seen some winners--like "Arracame La Vida" and "Don't Let me Drown"...and some whose story or "message" was garbled or just plain too obvious.