One of the Bible passages often cited by modern Lutherans in an attempt to prove that all people have already been justified is 2 Corinthians 5:19. They point especially to the phrase "not imputing their sins to them" ("them" being "the world"). Since the Apostle Paul equates the non-imputation of sins with justification in Romans 4:5-8, they claim that this means that the whole world has already been justified.
But it couldn't be more clear that when Paul speaks of the non-imputation of sins in Rom. 4:5-8, he is referring only to those who have faith, for "his faith is accounted for righteousness."
There are two possibilities here. Either (1) Paul is using the exact same language to describe two different "events," one justification that took place at the cross of Christ without the ministry of the Word and not through faith (2 Cor. 5:19), and another justification that only takes place through faith (Rom. 4:8). Or (2) Paul is using the exact same language to describe the exact same thing, that God does not impute sins to believers in Christ. In other words, justification only through faith.
Luther, Chemnitz and Melanchthon did not see any world justification in 2 Cor. 5:19. On the contrary, they saw Paul highlighting the ministry of the Word and teaching justification only through faith in Christ.
Here follows an excerpt from Philip Melanchthon's 1523 commentary on this verse. Notice to whom God does not impute sin.
Annotations on Paul's Epistles: One to the Romans and Two to the Corinthians
(with introductory letter by Dr. Martin Luther)
2 Corinthians 5:19
…not imputing their sins to them.
This demonstrates what the effect is of the reconciliation made by the Son. For since God the Father transferred the sins of us all from us to the Son so that He might pay for us the penalty for sins and in this way reconcile again the offended Father, the eternal Father now does not impute sins to those who believe in His Son; He regards them as righteous on account of the obedience and intercession of His Son. For the righteousness of man which God regards as righteousness is that sins are remitted, are not imputed and are covered, as Paul defines righteousness in Romans 4, citing Psalm 32. Therefore, the effect of reconciliation is that sins are not imputed; instead, the faith that embraces Christ the Reconciler is imputed for righteousness.
And He placed among us, etc.
That is, He instituted the ministry of teaching about the reconciliation made through the death of the Son. For God wants it announced to the entire human race that reconciliation has been made by the Son, so that sins are not imputed to believers; instead, righteousness is imputed to them, and thus believers are saved. For this reason, among the ruins of the empires and so many sects and heresies, God has to this day wondrously preserved this ministry, and will continue to preserve it until the end of the world and the advent of His Son, as Paul says, “You shall announce the death of the Lord until He comes.”