Galatians 2

Now when Peter had come to Antioch, I withstood him to his face, because he was to be blamed;  for before certain men came from James, he would eat with the Gentiles; but when they came, he withdrew and separated himself, fearing those who were of the circumcision. And the rest of the Jews also played the hypocrite with him, so that even Barnabas was carried away with their hypocrisy. vv.11-13

Read chapter 2
Hypocrisy.  It's a thing that can really turn someone off or closed to a matter.  No one like a hypocrite yet we all are hypocrites at some time or another.  Here Paul is mentioning the hypocrisy of Peter, one of Christ's apostles, and calling him out in it.  Peter would eat with the gentiles but when certain men, strong followers of Jesus, came around he pretended like he didn't even know the gentiles and wouldn't associate with them.  And this act of Peter led others astray to act hypocritical as well.  I don't know what hurt more: the gentiles feeling betrayed by Peter when he acted this way or the guilt of Peter on himself or these other men feeling and knowing they've been lied to by their fellow brother in Christ.  This specific hypocrisy seems so childish and like a typical teenage issue in schools today of wanting to be popular so one denies certain friends.
Many nonbelievers don't want anything to do with Christianity because they see the hypocrisy of Christians.  We have to realize we're been watched extra closely for any slip up, not that believers never sin but do we live in hypocrisy or confess our wrong when we mess up.  
When have you played the hypocrite?  How can you change that so you live a life of truth?