Augustine on confronting the sins of others:
We should never undertake the task of chiding another’s sin unless, cross-examining our own conscience, we can assure ourselves, before God, that we are acting from love. If reproaches or threats or injuries, voiced by the one you are calling to account, have wounded your spirit, then, for that person to be healed by you, you must not speak till you are healed yourself, lest you act from worldly motives, to hurt, and make your tongue a sinful weapon of evil, returning wrong for wrong, curse for curse. Whatever you speak out of a wounded spirit is the wrath of an avenger, not the love of an instructor… And if, as often happens, you begin some course of action from love, and are proceeding with it in love, but a different feeling insinuates itself because you are resisted, deflecting you from reproach of a man’s sin and making you attack the man itself — it were best, while watering the dust with your tears, to remember that we have no right to crow over another’s sin, since we sin in the very reproach of sin if anger at sin is better at making us sinners than mercy is at making us kind.
~From Commentary on Paul’s Letter to the Galatians, cited in Jonathan Leeman’s The Church and the Surprising Offense of God’s Love: Reintroducing the Doctrines of Church Membership and Discipline