I thought this was a good documentary that made a lot of good points. The primary one being that those who profess Christianity give it a really bad name by their very unChristian attitudes and behavior, i.e. condemning homosexuals instead of reaching out to them with the good news of the gospel. HOWEVER, his premise is wrong from the start. He assumes that all of those who call themselves Christians actually are. Going to church, calling yourself a Christian, saying a prayer, etc does not a Christian make. It is God alone who saves. Not us by our prayers and our decisions. When He saves us, He changes us. He makes us more Christ-like.
You will know a Christian by their fruit. By their compassion, humility, joy, mercy, and repentance.