We deserve judgment, and we don't need some fire-breathing evangelist to tell us that because we know it in our hearts and our own conscience condemns us, though usually for different reasons. We go out to God's other creditors, and we offer them grace. We have no right, but we do it anyway. And instead of punishing us for such audacity, offering grace to sinners, God commends us. Thus, the dishonesty of the story is precisely the point.
Grace is unfair.
We don't deserve it. We waste it when we get it. But God is pleased to give us more grace anyway, even to commend us for letting others off the hook, too. And we don't want to tell this to our children whom we are trying to raise right to be honest and good and just in their treatment of others and to understand the consequences when they don't. But the truth is, most people don't get what they deserve.