At the cross, Jesus Christ defended God's Righteousness (Rom. 3.25).
There were (and are) those who would say that God can forgive sin without blood, without wrath, without payment. Brian MacLaren is one contemporary voice in that camp. My issue with that thought is that it's simply not biblical. Other than that, I'd love to have a God who wasn't particularly amped up about blood and justice and sacrifice.
But God cannot sweep sin under a cosmic rug. And He doesn't. The righteousness of God needed a "defense" (used loosely) against the accusation that the sin forgiven for the OT saints and the sins to be forgiven for all of us were wiped away without payment, without justice, without an exaction.
But here, in what some call the most important paragraph in the Bible, we see God's intent. He passed over sins formerly committed to display His righteousness at the proper time (at the cross) and thus display Himself as the Righteous One and the Righteous Maker of the ones who have confidence in Jesus.
Jesus took sin upon Himself so we didn't have to bear the wrath of God. That's something to revel in.