You leave out the critical question: how do we best protect society? The cycle of abuse, and circumstances that explain how abusers become abusers, does not absolve us from the necessity of protecting potential victims. It does, however, forces us to treat inmates humanely and to not engage into pure 'retaliation'. There's little evidence that punitive sentences actually do anything for preventing crimes. You can acknowledge the dangerousness of specific individuals and the necessity of preventing (further) crimes, while understanding how they got there.

It's also critical to intervene early. By the time they're adults, or have started a criminal career, it's much more difficult for someone to change. At this point potential sentences, however 'punitive', do very little dissuasion.