If you think it’s always wrong to go to R-Rated movies, what do you make of a historically realistic movie about Jesus that is about to become the most successful R-rated movie in history. This is a prime example of how legalistic ethics break down. Rules are fine but must be applied in context. Rules attempt to say what should happen in all situations but what happens when a situation pits two rules against each other. Then you must decide in that context which rule takes precedence. I think this is what Jesus meant when he talked about the weightier matters of the law.
You practice making ethical choices by constantly examining context to see if your rules conflict or if your rules are overturned by a new context. Many R-Rated films are polluting to the soul and a rule to avoid them is a good idea. But blindly applying that rule regardless of the context foolish. Some would say that The Passion should have been rated NC-17 because of violence. Others might say that all religious films of this kind should be banned because they promote intolerance and violence. The great irony is that often those who 'religiously' avoid R-Rated films are at the same time reading a Bible that is very much an R-rated book (as The Passion proves). What I'm advocating is a more penetrating look at context to force introspection about how and when to apply rules and sometimes, when the rules need to change. The fact that this is a complex and difficult process is no reason to abandon it. Wisdom depends on it.