Reading this discussion a few ideas come to my mind:
1. The simple idea of retaliation ("talio" which is basically "an eye for an eye..."), driven by a feeling of need for revenge is never going to bring any good. And in fact I don't think any American would think that whoever did this should be paid back evenly. No or only very few Americans would feel it justified that innocent people would have to be punished in an attack on civilians in order to "get even". So in fact we're all not that far apart in this discussion as it sometimes seems to be.
2. Revenge in the name of God which I sometimes sense in expresions like "God bless America, God bless the US Army" is in fact the same kind of fundamentalistic thinking as Muslim terrorists use to justify their deeds. I do not believe revenge is the right kind of motive to react to the crimes committed on Tuesday. However, military actions that are sharply focused on eliminating the driving forces behind them seem justified to me. But if revenge becomes the primary motive, an endless chain of violence will be the result. And if there's a devil I'm sure he's going to have the time of his life then.
3. Christianity has had its excesses in its history, but in modern times I see only one religion where fundamentalism leads to the excessive use of violence. (Northern Ireland is NOT an example of fundamentalism, as was stated in one earlier post.) And that is Islam.
As far as I know and can find out, Islam arose in the 7th century, when it was founded by Mohammed, who opposed to Arab idolatry, as well as to the Jew's rejection of Jesus and their nationalistic concept of their religion, as well as to the Christians' ideas of Trinity and of crucifiction.
Just as Christianity and Judaism have had their periods of violence in past ages, Islam seems to go through such a period now. Islam is in my view still stuck in the Middle Ages, the horrible thing however is that they use modern means of violence.
4. The American people profile themselves as a Christian nation. And indeed what we call modern civilisation nowadays is imo totally based upon Christianity, despite growing secularisation in the western world. The values that we want to defend are deeply rooted in Christian ideas.
5. If we feel that modern western values need to prevail over muslim terrorism and fundamentalism, our response to terrorist acts should be in accordance with the values that we claim to defend. Blind violence to retaliate or revenge means essentially falling in that same trap of fundamentalist thinking, especially if it is done under the idea of "God being on or side". A moderate military reaction that only hits those responsible would be worthy to the modern western civilisation. However, bringing them to justice without a military action, would be the best triumph that one could wish for.
6. If we believe that Christianity has a better perspective on the human existence than Islam has - and I personally believe so - than we should do every effort to base our actions on the values which that same Christianity has taught us, even if we feel that those values have been brutally violated. This would also be the best missionary action that I can think of, as the spreading of leaflets and videotapes (German aid workers in Afghanistan) does not seem to be very effective.