"When we judge other people we confront them in a spirit of detachment, observing and reflecting as it were from the outside. But love has neither time nor opportunity for this. If we love, we can never observe the other person with detachment, for he is always and at every moment a living claim to our love and service...
Judgement is the forbidden objectivization of the other person which destroys single-minded love. I am not forbidden to have my own thoughts about the other person, to realize his shortcomings, but only to the extent that it offers to me an occasion for forgiveness and unconditional love, as Jesus proves to me. If I withhold my judgement I am not indulging in tout comprendre c'est tout pardonner and confirm the other person in his bad ways. Neither I am right nor the other person, but God is always right and shall proclaim both his grace and his judgement.
Judging others makes us blind, whereas love is illuminating. By judging others we blind ourselves to our own evil and to the grace which others are just as entitled to as we are. But in the love of Christ we know all about every conceivable sin and guilt; for we know how Jesus suffered, and how all men have been forgiven at the foot of the cross. Christian love sees the fellow-man under the cross and therefore sees with clarity. If when we judged others, our real motive was to destroy evil, we should look for evil where it is certain to be found, and that is in our own hearts. But if we are on the lookout for evil in others, our real motive is obviously to justify ourselves, for we are seeking to escape punishment for our own sins by passing judgement on others, and are assuming by implication that the Word of God applies to ourselves in one way, and to others in another. All this is highly dangerous and misleading. We are trying to claim for ourselves a special privilege which we deny to others. But Christ's disciples have no rights of their own or standards of right and wrong which they could enforce with other people; they have received nothing but Christ's fellowship. Therefore the disciple is not to sit in judgement over his fellow-man because he would wrongly usurp the jurisdiction."
From Cost of Discipleship by Dietrich Bonhoeffer. pp. 184, 185