"Judge not, lest you be judged; for with the measure you use, it will be measured to you." -- Jesus
In my experience, this saying of Jesus is misused more than many others. Every defiant sinner takes up "Judge not" on his or her lips as a shield against criticism. When Jesus taught the Sermon on the Mount, he kept coming back to the point of mercy and humility towards each other. It's a lesson we all need. Mercy is, in its way, a shield against the Law. But it is a shield against its condemnation, not against its rightness. "Judge not" should keep the one who points out wrong away from hypocrisy or pride or setting himself up as a judge; it should not excuse the wrongdoer or obscure whether a thing is right or wrong.