"I have made my peace with the ‘Man upstairs.’"
When people refer to God as "the Man upstairs," they reveal that they have no concept of (nor living relationship with) Him. They will use such words because they feel uncomfortable saying His name. Often they will have a measure of reverence for God, but not enough to obey Him.
Ask if the person thinks he will go to heaven when he dies. He’ll almost certainly say he will, and a little probing will reveal that he’s trusting in his own goodness to save him. However, the only way sinners can have peace with the God they have offended is through the shed blood of the Savior. Therefore, it’s important to take the person through the Ten Commandments and strip him of his self-righteousness and his false sense of assurance of salvation.
As you do so, you may feel bad that you are making him uncomfortable, but if you care about his eternal salvation, you must ask yourself, "Which is worse: a few moments of conviction by the perfect Law of God, or eternity in the Lake of Fire?" Unless there is a knowledge of sin (which comes by the Law—Romans 7:7), there will be no repentance.