I wrote a short article for Christianity.com asking the question, "When should you correct another Christian?" You can read it here.
It's certainly a good question to think about. Correcting and receiving correction is a vital part of the Christian life. What good is a discipling relationship that doesn't include lovingly point out sin? After all, sin unchecked may be evidence of an unregenerate heart.
But there are times to overlook the sins in others, too. So I address that as well. In a nutshell, I'm thankful for the brothers and sisters who point me to my sin and I'm thankful for the way they so often overlook my sin. Both actions are evidence of the gospel at work in their life and in mine.