I haven't read Hauerwas, but I am inclined to feel the same way as you have expressed it here. To claim that Christ has already ended war it to deny the horrible military conflicts that are occurring even now. On the other hand, I do think that we are in a day in which we Christians must stop talking about "just war." That whole just war theology was an accommodation to political powers and human failure. Especially in this day of nuclear armament, the church must be a prophetic voice to call for better ways to settle conflicts. The Quakers, Amish, and Mennonites have succeeded in opting out of war, and they bear witness to that vision of peace that Hauerwas seems to appeal to.  For humanity to succeed, we must put war behind us - but we are not there yet. As long as Christians continue to claim that their country is justified in taking up arms, we will not get there.