spoilers and all
There are many films that feature not merely "righteous" violence, but "redemptive" violence. That is, a violent act becomes a necessary, regenerative, redeeming act; within the narrative and within the context, violence is an obvious and successful solution to a threatening problem. In the film's narrative, violence works to bring about the good it intends.
Gran Torino appears that it may follow the redemptive violence myth. Walt Kowalski is repeatedly successful when he uses the threat of violence to defend innocent, threatened people. However, the real success of Walt's transformation is not in his use of violence to protect the innocent, but in the relationships he builds, particularly with Thao and Sue Lor. He becomes heroic not because he's willing to violently destroy evil, but because he becomes willing to build friendships, engage with people. The motif of the tools is important: it is easier to destroy than to build, but building is what matters. He helps Thao by teaching him, by providing for him. The middle of the film is devoid of much violence at all, and that is when Walt is able to do good.
But in this peaceful middle, Walt has not given up his belief in regenerative violence. When Thao is again harassed, Walt goes violently after one of the gang members that harasses him. He violently beats the man, tells him to leave Thao alone, and threatens him with further violence. What happens, however, of course does not end the violence. The gang shoots up the Lors' home and beats and rapes Sue. Violence begets violence.
Walt realizes the role he played in this cycle, how his own violence makes him responsible for what happened. When he sees Sue, he drops his drink, goes home, and begins mutilating his fists by punching through glass. Given that Walt is clearly dying, a viewer may now expect the violent shootout in which Walt nobly and bravely sacrifices himself to help Thao and Sue. Sort of. It is not redemptive violence, but redemptive self-sacrifice: Walt goes unarmed, allowing himself to be murdered so that the gang would be imprisoned. He uses the final shootout scene not to wage righteous violence, but to bring about redemption through sacrifice.
Now, the image of the selfless hero sacrificing his own life for the greater good (often with explicit Christ imagery) is not new in art: the very violent Matrix trilogy ends with peace, not destruction, brought about when Neo sacrifices himself and, indeed, finds himself sprawled out on screen as if crucified. Reading Ken Kesey's One Flew Over the Cuckoo's Nest, the comparisons of Randle Patrick McMurphy to Jesus become almost a bit much. It may even be that this has become a tired, repetitive, uncreative image. It is, however, a story worth repeating, especially in American film: if the deconstruction of the redemptive violence myth seems itself overplayed, it is only because the redemptive violence myth is even more overplayed.
And while Christians often seem to perpetuate and encourage the redemptive violence, it seems rather obvious to point out that the story of Jesus's life is one of redemptive self-sacrifice. In The Politics of Jesus, John Howard Yoder writes that Jesus explicitly rejected the "Zealot" option of violence. Indeed, when Peter tries to violently defend Jesus against arrest, Jesus stops him, telling him that living by the sword means dying by the sword (in other words, violence begets violence). I'm afraid that given a different context, many American Christians today might defend Peter's actions, seeing his violent self-defense as entirely justified (I can't stomach a serious response to this). But Jesus offers a different message: that redemption cannot come through righteous violence, that waging violence does not bring about salvation or peace. That message is in direct conflict not only with many violent films, but with the logic that justifies perpetuating America's current wars.