First of all, this is not a Christian movie. It is a movie about a Christian.
If this had been a Christian movie I would rate it lower due to the minimal portrayal of the gospel. This movie presents a glimpse of the persecution awaiting true followers of Christ who refuse to recant their faith.
Second, the MPAA rating is for language. The captors use a lot of F bombs. This is not a movie for younger children.
Third, regardless of content, if you are a Jim Caviezel fan, you must have this for your collection.