I highlighted the distinction I see between atonement for sin, and the forgiveness of sin. Let me see if I can expand upon this. The Hebrew scriptures clearly state that the sinner is held accountable for his own sin. So how can one understand the sacrifice Jesus made of himself, without viewing it as a vicarious atonement? I think that passage from Paul points to another way of looking at it.
God desires to reconcile the world to Himself. Jesus, in freely laying down his life, "incarnates" or makes present God's love for us. He saves the lost by revealing the light of the Father's love. When we then repent and turn to God for forgiveness, God does not count our trespass against us, but like the father of the prodigal son, welcomes us back with open arms.
In a sense, you could say that Jesus's purpose what to reveal that God's love and forgiveness are so superabundant that we don't need to atone for our sins! We simply need to repent and ask forgiveness -- then go and sin no more. A light yoke indeed.
This makes sense to me. Jesus said that he came not for the well, but for the sick. Not to call the righteous, but for the sinners. Those who were lost -- so lost that they didn't think they could be forgiven.
For I desire steadfast love and not sacrifice,
the knowledge of God, rather than burnt offerings. (Hosea 6:6)
He has showed you, O man, what is good;
and what does the LORD require of you
but to do justice, and to love kindness,
and to walk humbly with your God? (Micah 6:8)
I will heal their faithlessness;
I will love them freely,
for my anger has turned from them. (Hosea 14:4)
This was Jesus's message.
If it helps any, consider the Catholic notion of actual righteousness, as opposed to the Protestant notion of "assumed" righteousness.
To the Catholic the righteousness which is counted toward the person is an actual one made possible through the grace of Christ. Christ's perfection does not become a substitute for my own, but becomes the impetus behind my own real perfection.
This is then judged and my perfection is seen as good.
Those who do not follow Christ end up as wicked as they began. So truly:
the righteousness of the righteous shall be upon himself, and the wickedness of the wicked shall be upon himself.
SD