If we can forgive without accepting, a lot more becomes possible.
"To forgive", in this context, should be understand in the same word as "debt forgiveness" - which means, nothing will change that you ran up a debt, but I waive my right to collect on that debt. It is not right that you ran the debt up, but I have decided that it's in everyone's best interest not to pursue it.
Note that we can forgive, not that we must or should. We have a choice of actions, we can pursue debts or forgive them. Which ties into the broader mystical frame that "God is both just and merciful". "Just" might mean: "everyone gets what they deserve". Mercy means: "everyone gets more than they deserve". Since we are all sinners and black sinners (or to put in secular language, we are all weak and forgetful and make mistakes), then we had better hope that others practice mercy; and indeed, an eye for an eye leaves the whole planet blind.
"Forgiving without accepting" means "exercising mercy while recognizing that it contradicts justice". In the outcome of that contradiction lies an ethical framework for a free humanity. The whole concept of restorative justice relies on precisely this question of giving the victims of a crime their own free choice as to what blend of mercy and justice should be pursued.