Matthew 7

do not judge, or you too will be judged.
we arent perfect! the blood of Christ has made us righteous, but we still can sin, and we have sinned. it's always in us to want to tell others off, but we must do so in love, or we will become hypocrites! why hypocrite? because very often the mistakes we spot in others are because we have them ourselves. its magnified so much because we know whats in us and we tend to 'look out for it', whether subconsciously to make our own faults seem normal.
judge yourself first, and you will find that you are guilty of the same thing, maybe not exactly the same situation, but just change the objects, change the setting and voila, there you are in exactly the same sin. God will be the judge, so let's leave Him to that. but that doesnt mean neglect the sinner, please help him to stop sinning! especially since now you've found common ground and can relate to him :P