For the benefits of those new to the debate, I'll repeat the standard response from pro-war Catholics facing criticism for dismissing the Church's position. (You can say it with me if you like. Maybe it should be set to music and made into a hymn).
The Church's position on the war is a matter of prudential judgement, not a statement of doctrine, and thus does not require the assent of the faithful.
Another problem I have with this is people measuring themselves by what is "required." Cathoics are also only required to go to confession and recieve the Eucharist once a year, but I think most of us know that we should recieve those sacraments more often in order to live a life of holiness.
One of the big things Jesus was about was calling us to a positive morality of love rather than a legalistic morality of staying withing the Law. Obeying the Commandments are important, but it's a bare minimum of what we're called to do.
A lot of the pro-war Catholics say that those who agree with the bishops and the Holy Father fail to think for themselves, and are guided by a warped sense of personal loyalty to the Holy Father that is inappropriate. But then they hide behind this legalistic statement in order to answer any objections that maybe the arguments they're using aren't all the helpful to the Church, and could cause long-term harm to the Church's ability to teach.
Who is really thinking for himself? Who is engaging his conscience? The person who uses this "prudential judgement" loophole to make broadside attacks on the Church's teaching authority, or the one who doesn't see the difference as a license to harm the Church?