I may have overlooked it. If you would like to point me to it, I will certainly consider it.
Penalty substitution advocates use 2 Corinthians 5:21, that “God made Him who knew no sin to be sin on our behalf, so that we might become the righteousness of God in HIm,” to support the concept of double imputation, that our sin was imputed to Jesus so that his righteousness could be imputed to us. They want the verse to say something like, “He made him who knew no sin to be
sinful (or guilty of sin by imputation) on our behalf so that we might receive the
righteousness of Christ from him (modifications in italics),” but this is not what the text says. NT Wright’s commentary on this verse is very helpful. In the second part of the verse, the phrase “the righteousness of God” does not mean “the righteousness of Christ,” which would refer to the Messiah/Son’s legal status of righteousness. The “righteousness of God” refers, again, to God’s covenant faithfulness to bless all nations through Israel. When Paul says, “we become the righteousness of God,” he is saying that the people of God, the Church in Christ, has become an outworking, demonstration, and manifestation of God’s faithfulness to His covenant promises. Paul is not talking here about the imputation of Christ’s legal status of righteousness to us.
If Paul is talking about a demonstration or manifestation rather than an imputation in this second part of the verse, it follows that he is doing the same thing in the preceding half of the verse, in which he says “God made him who knew no sin to be sin”. Paul is not saying that our sin or guilt was imputed to Jesus, but that the sinless man Jesus was made into an outworking, demonstration, and manifestation of our sin. This certainly describes the cross. The cross is the greatest sin in human history, in which all sin against God and all sin against Man are inflicted upon the God-Man Jesus Christ. No sin that any of us has ever committed is greater than the sin we committed when we crucified Jesus. The worst aspect of any one of our sins is that it contributed to the death of God’s Son. On the cross, Jesus was made my sin. He was made into a demonstration of every human’s sin. Why? So that through Jesus’ resurrection, God would show His faithfulness to his covenantal promises to restore the earth from sin’s destruction.
So here is a paraphrase of the verse: God made Jesus, who knew no sin, to be made a manifestation of sin on our behalf, so that we sinners could, in Christ, become the manifestation of God’s covenant faithfulness. As NT Wright says, “God made [the Messiah] to be sin on our behalf, so that in him we might embody God’s faithfulness to the covenant.” (Paul and the Faithfulness of God p.20) NT Wright makes the argument also in Resurrection of the Son of God:
Remember the question that is always in the back of Paul’s mind, as well as his Jewish audience: “God, how are you going to prove yourself faithful to your promise to bless all nations through Israel, given that Israel is a nation of sinful human beings?” Paul’s answer here is that, just as God used a sinless person to demonstrate the sinfulness of humanity, so also God uses sinful human beings (in this case the church as the new Israel) to demonstrate His covenant faithfulness.” Humanity’s sin was proved through the cross, and God’s faithfulness is proven through the church.
A couple analogies: Consider the photograph of "Whipped Peter" that was printed in major newspapers preceding the abolition of slavery in the United States. It is a photo of a slaves brutally scarred back. You could say that Peter "became America's sin." Many people finally understood the horrors of slavery when they saw that photo, all the sin was summed up in that one image. Or think of Emmet Til, the young black boy who was brutally tortured and murdered, and whose photo was widespread as a testament to American racism. Emmet Til "became America's sin."