Andrew, thanks for your generous reply to my comment on this difficult subject. A few additional remarks:

1) Your clarification of what you meant by "moral complacency" and "theological superiority" is helpful. I agree that it is important for Christians not to assume that their convictions are superior to those held by non-Christians. I am reminded of the postmodern critique of metanarratives as imperialistic.

2) Perhaps apparent discrepancies between the Old Testament and the New Testament on this subject are exaggerated. I am coming out of a background in which the idea that there were any discrepancies between the two testaments was condemned. At this time, I am content to accept that there is both continuity and discontinuity between the OT and NT (N.T. Wright’s work has been helpful to me here). I was quoting Richard Hays when I wrote of "irreconcilable tensions"; in context, Hays is discussing Christian ethics. He is arguing that the NT’s attitude toward the use of violence by God’s people is different than the OT’s attitude toward the use of violence by God’s people. This difference does not rule out the possibility of interpreting Rome’s violence against Jerusalem as God’s judgment; it would seem to fit with Paul’s instruction in Romans 12 to leave vengeance (and its violence) to God. It’s an exegetically sound conclusion. However, it poses missiological problems. Here in the U.S., some preachers boldly called 9/11 and Katrina God’s judgment on America; in doing so, they gave non-Christians and nominal Christians more reasons to avoid the church.

3) I most appreciate your last paragraph:

But it appears, in the end, that we are more or less in agreement. The moral and theological problems remain - and perhaps they should be a thorn-in-the-flesh to us. I don’t think that we can with integrity affirm the ideal character of Jesus without acknowledging the part that violence places in the biblical story, which is Jesus’ story. The calling of the new covenant people of God, however, is absolutely to renounce violence, to demonstrate to the world that within the confines of new creation justice can be achieved by peaceful and compassionate means, even if at times that will require extreme self-giving.

Violence is an undeniable part of the biblical story (which is part of what makes it realistic—we live in an undeniably violent world, after all). Followers of Jesus are called to renounce this violence. Though Jesus does not restate or otherwise affirm them (thankfully), retaining the conquest narratives of the OT remains necessary, as the story of Israel would make less narrative sense without them. They are descriptive rather than prescriptive, however. Still remaining is the problem of what they communicate about God’s character—here they are "a thorn-in-the-flesh to us."