A pointed rebuke, apart from the proclamation of redemption, is not yet the preaching of repentance, but is simply the accusation of the Law, which exposes sin, burdens the conscience, and drives man to despair. This work of the Law is necessary, but, by itself, it is not able to bring about repentance. For true repentance comprises not only sorrow for sin, but also confident trust in the Lord's mercies.
In confronting an individual concerning a particular wrong, it may be that he remains recalcitrant and stubbornly persists in his sin. In such a case, he should be admonished and rebuked with the Law, but not absolved or consoled with the Gospel, until his prideful heart is broken by contrition. That does not call for a reading of his heart, but for his acknowledgment of sin and sorrow for it, and a fleeing to the Lord for mercy.
In offering an open rebuke, however, whether in preaching to the congregation, or in public discourse online or elsewhere, there must needs be the preaching of Christ and His Redemption of the world. The preacher does not presume upon anyone's heart, whether for good or ill, but proceeds in the confidence of the Word of the Lord, both the Law and the Gospel, that these will accomplish the purpose for which they are spoken.
The sharp sting of the Law, which pierces the heart and soul of the sinner, and slays the old Adam in his sin, is to be accompanied by the sweet savor of the Gospel, which heals the brokenhearted and comforts the terrified conscience, setting the sinner free from guilt and shame through the Cross and Resurrection of Christ Jesus. For God was in Christ reconciling the world to Himself, not counting men's trespasses against them. It is by the preaching of this Gospel that true repentance is accomplished and brought to completion through faith in the forgiveness of sins.