God is both righteous and He is just. We all have sin, which requires justice (in the same way that heinous crimes have a consequence and punishment...a judge in court would not be serving justice if he were not to sentence a crime that was committed...justice would not be served, and he would be a corrupt and immoral judge). God is not unjust or immoral. God is Just. BUT God is also righteous and loving, so the payment of sin, which is death, was taken by Christ. Christ received death not just physically, but spiritually. In the moment that Christ was on the Cross, the spiritual wrath of God was placed on Christ. He experienced the agony of God's wrath for the sins committed by man.

God Himself took the punishment that is required for justice to be served, while simultaneously committing the most loving and self-sacrificial act imaginable. Christ lived a perfect and sinless life, what we are incapable of doing, and was completely blameless...and yet had the sins of man imputed upon Him, while His righteous was imputed on us. The balance was then paid. Once imputed with His righteousness, we are now seen as blameless before God. His sinlessness, through His act of atonement, was transferred to us, it is credited to our account because the payment was made for justice to be served.

This does not give us a license to sin, or to continue doing what we are doing scott-free....once you realize the magnitude of the act performed on our behalf, you will no longer want to sin, and will respond with praise and gratitude at the realization of your redemption, and how undeserving you are of it...and how merciful and sacrificial it was for Him to pay the price for you when He didn't have to, for no other reason than out of love for His own children. Many parents would take a sacrifice for their children...and what God did is infinitely greater. He took the punishment for all the sins of man.