(see this post and comments section for the first part.)
OK. I've asserted that it may be not only permissible, but also beneficial, for Christians to watch movies or read books without an explicitly Christian worldview -- even books or movies whose themes oppose a Christian worldview, or that are anti-gospel.
Let me add one more assertion: I think it is the height of folly to judge a book or a movie based on what it omits rather than what it affirms. Again, the Twilight books demonstrate how this happens. Edward and Bella, the two main characters, refrain from sexual intercourse until they are married, at Edward's insistence (leaving aside for the moment that he does so because he fears he will be unable, in a state of arousal, to keep control of his desire to kill Bella. And that she, knowing this, keeps pushing him to have sex with her). I can't tell you how many times I heard, from the girls at my school or from Christian parents of my acquaintance, "Well, it can't be that bad; at least they stay pure until they're married! It's a good example to teenage girls!"
Do I dare insult your intelligence, dear reader, by pointing out the folly of ignoring an onslaught of insipid prose both describing irreparably twisted relationships and suborning heresy because the two main characters narrowly and for the wrong reasons avoid one form of immorality? By all means, read insipid prose describing twisted relationships and suborning heresy if you identify them all as such. But don't pretend that it's "not so bad" as you stretch out on your blanket in the park for a sunny afternoon's passive absorption of insipid prose, twisted relationships, and heresy.
I'd much rather my students come to class and say, "Miss Roberts, we watched Massive Gory Shoot-Em-Up: Part IV on Friday night and, geez, it was so wrong! I couldn't believe how Studly McHotness treated women! And the way women threw themselves all over him even though he was a total dirtbag... ew. I thought it would be cool, but I just couldn't get into it," than, "I went shopping at the Christian bookstore and bought this great new book -- I'm A Christian Princess! It's all about how God is the king of everything and that makes Christian girls princesses, so we should make sure that everyone treats us like princesses! Isn't that right?"
Christians cannot avoid evil, and we must not pretend it doesn't exist. Whether non-Christian media, and its depiction of evil, hardens our consciences toward the real thing or trains us to address the real thing depends on how we approach it.
I think the first step is to ensure that we and the young people in our care are absolutely crammed full of Bible. God's Word contains everything we need for godly lives, but if we don't know it, it's of no use to us. Why are there so many stories in the Bible? I think it's so that, when our life stories start to run along the same lines, we'll know the outcome of certain actions. We don't have to come up with an object lesson to teach young men not to ogle naked chicks. We just have to send them to the story of David and Bathsheba!
Beyond the Scriptures, God has given humanity two priceless teaching tools: a colorful and checkered history, and an irrepressible urge to write stories. In these we see an affirmation, whether intended or not, that God's word is true.
As N.D. Wilson puts it, my goal is for my students to learn to recoil from sin, to see in the Scriptures and in fiction and history a tiny taste of the fires of Hell. I want my boys to be so familiar with Lady Folly and Becky Sharp and the Green Knight's wife and Anne Boleyn and Mata Hari that they learn down to a fundamental, instinctive level to stay the heck away from the house of the seductress. I want my girls to know Mr. Rochester and the Highwayman and Count Vronsky and John Wilmot well enough to recognize the sort of twisted romantic obsession that drives women to forsake -- or nearly lose their lives to keep -- their most dearly-held principles.
This sort of education will, ideally, have two results. First, it will enable them to recognize good and evil in fiction. A young man who recoils from Mata Hari will have no trouble recoiling from Our Mrs. Reynolds. A young woman who learns to despise the Highwayman instinctively will hardly be fooled by the endearments of the be-sparkled Edward Cullen.
Following on from number one, this sort of education enables them to recognize good and evil when they encounter it in real life. Again paraphrasing N.D. Wilson, I want my students to know that if the Fool follows the Seductress to her house on page 4, on page 10 he's going to get way more than he bargained for. I want them to know that judgment follows sin as surely as B follows A, and I don't want them to have to learn it the hard way.