How can I explain to my teenage son that watching movies like "The Dark Knight" is not God-pleasing or that he should avoid and turn away from watching movies with sex or bad language and violence. He just watches them and thinks it's okay--he thinks nothing is wrong with watching a movie for entertainment. It is corrupting your mind and can lead to thinking it's okay - can't it?
Watching a movie for entertainment is fine, but “entertainment” does not make objectionable content acceptable. Your concern for your son’s welfare is good and commendable.
You can explain to your son that sexual themes in movies can do much to degrade women, glamorize adultery and desensitize Christians to sexual sins. What may appear to be mere entertainment can definitely adversely affect a person’s thoughts and words and actions.
You can remind your son that the wrong kind of entertainment can fuel sins against the sixth commandment. Jesus said, “You have heard that it was said, ‘You shall not commit adultery.’ But I tell you that anyone who looks at a woman lustfully has already committed adultery with her in his heart” (Matthew 5:27-28).
Similarly, being exposed to crude and vulgar language in entertainment can have an effect on Christians and the way they talk. God gives this directive: “Nor should there be obscenity, foolish talk or coarse joking, which are out of place, but rather thanksgiving” (Ephesians 5:4).
Recognizing that the images and sounds that reach our minds can affect us, it is no surprise that the Bible gives this instruction: “Finally, brothers and sisters, whatever is true, whatever is noble, whatever is right, whatever is pure, whatever is lovely, whatever is admirable—if anything is excellent or praiseworthy—think about such things” (Philippians 4:8). It would be helpful for Christians of all ages to ask themselves if the entertainment they are engaged in passes the “Philippians test.”
God bless you and your family as you seek to be salt and lights to others around you (Matthew 5:13-16).