an old internecine Catholic argument

Still being waged, apparently. I suppose we need to try to be more persuasive. In short, the argument is this:

There is no Catholic judgment on the war in Iraq. There are Catholics who have judgments, but none of these judgments is Divinely sanctioned. The Church teaches faith and morals - principles of dogma and principles of morality. Whether Iraq was a just war or not is not a question to which the Church supplies an answer.

We ought to listen attentively and with our whole heart to the humble and holy servant of God who currently occupies Peter’s chair, but we will not always have a wise pope. We have had and may very well have again evil popes whose judgments about war and other major contemporary issues will be deeply and obviously flawed. The gift of infallibility does not necessarily include the gift of wisdom.

Catholics of good faith can and do disagree about complex prudential questions. Further, we ought to be weary of the authoritarian cast of mind that would make everyone submissive to every thought and whimsy of the Pope. There is a great temptation in trying to give one’s opinions the force and weight of the Divine.

This is why it is important to be able to make a distinction between a question of principle and a question of the application of principle - if we lack this ability, we lack the ability to understand the nature of the Church’s teaching, which is another way of saying we lack the ability to understand a tremendous gift.

C.S. Lewis said the same thing, but better, in an essay titled "Meditation on the Third Commandment". Here he is speaking on the the idea of a Christian political party:

It is not reasonable to suppose that such a Christian Party will will acquire new powers of leavening the infidel organization to which it is attached. Why should it? Whatever it calls itself, it will represent, not Christendom, but a part of Christendom. The principle which divides it from its brethren and unites it to its political allies will not be theological. It will have no authority to speak for Christianity; it will have no more power than the political skill of its members gives it to control the behaviour of its unbelieving allies. But there will be a real, and most disastrous novelty. It will be not simply a part of Christendom, but a part claiming to be the whole. By the mere act of calling itself the Christian Party it implicitly accuses all Christians who do not join it of apostasy and betrayal. It will be exposed, in an aggravated degree, to that temptation which the Devil spares none of us at any time --- the temptation of claiming for our favourite opinions that kind and degree of certainty and authority which really belongs only to our Faith. The danger of mistaking our merely natural, though perhaps legitimate, enthusiasms for holy zeal, is always great. Can any more fatal expedient be devised for increasing it than that of dubbing a small band of Fascists, Communists, or Democrats `the Christian Party'? The demon inherent in every party is at all times ready enough to disguise himself as the Holy Ghost; the formation of a Christian Party means handing over to him the most efficient make-up we can find. And when once the disguise has succeeded, his commands will presently be taken to abrogate all moral laws and to justify whatever the unbelieving allies of the `Christian' Party wish to do. If ever Christian men can be brought to think treachery and murder the lawful means of establishing the regime they desire, and faked trials, religious persecution and organized hooliganism the lawful means of maintaining it, it will, surely, be by just such a process as this. The history of the late medieval pseudo-Crusaders, of the Covenanters3, of the Orangemen4, should be remembered. On those who add `Thus said the Lord' to their merely human utterances descends the doom of a conscience which seems clearer and clearer the more it is loaded with sin.