Why is God just in judging Christ-rejecting men?
God is just in judging Christ-rejecting men because at the cross He paid every human being’s sin debt in full. Since that payment was made for all, those who reject it are judged righteously, not unfairly, as Paul affirms when he asks whether God is unrighteous to take vengeance. The answer is no.
Les explains from Romans chapter 3 that Paul raises the question: if our unrighteousness commends the righteousness of God, is God unrighteous who takes vengeance? Les emphasizes that God will one day pour out His wrath on Christ-rejecting men, but He is not unfair. The reason is that at the cross, every human being who ever lived had his sin debt paid in full. Therefore, rejecting Christ and His finished work leaves a person without excuse, and God’s judgment is just. The context also notes that the Jews had great advantages—covenant promises, the Old Testament, prophets, Psalms, temple, priesthood, and especially the oracles of God—but that does not change the universal provision of the cross.
But if our unrighteousness commend the righteousness of God, what shall we say? Is God unrighteous who taketh vengeance? (I speak as a man)