If there was any chance at all that the anti-war faction can win the day and thwart the war if only they can whip up the right number of protestors or make the right pleas, you would be correct. Then it would be possible for the Pope's position to support evil by allowing it to endure.
But there is no chance of this.
The Pope knows that America is going to go to take out Hussein and his supporters. The massive buildup is not there just for show, American resolve is cold and sure. So there is nothing for either the church or the US to gain from having the Pope endorse a war. It's already certain and what the Pope does or does not do will not alter the course.
At best the Catholic church could be more popular among say, US Marines if it said "Ooh rah, let's roll." But by endorsing our actions, the Pope wouldn't be giving us anything we need, nor would he be able to accelerate the pace towards liberation.
There is however, something to lose from endorsing the US position, and that is, unwittingly turning a war in which the US is seen as a liberator, into one in which the US will be perceived as threatening to impose the Christian faith on a mostly Muslim people. The imams and clerics would seem to be right, and they could more easily whip up fears of Americans, of occupation by "Christian zealots," etc.
So while it is evil to "do nothing" I might point out that it is also "evil" to do something which will make the right thing more difficult to accomplish. Sometimes you must do things which are difficult and in which you do not believe, in order to get closer to the right solution. Sometimes we're not even given the choice between good or bad, but only between bad or worse. That's what this country's founding father meant by the phrase regarding the sacrifice of "our lives, our fortunes, and our sacred honor." Sometimes, we must sacrifice even that in order to persevere in a righteous endeavor.
The jury is still out on whether or not that is what the Pope is doing. I cannot say what exactly the Pope is up to, if he is up to anything at all; some in the church have promoted communism in South America even as others fought it in eastern Europe, so I can only hope the Pope is still sound in mind. I'm not even Catholic, just a hot-tempered Lutheran who would prefer people say what they mean all of the time and not have to engage in intrigue. But I also know that we are not always given the choice of choosing between a principled position with no ill consequences, and pure evil with its inevitable consequences. Life isn't that easy; sometimes we must choose between maintaining our principles but getting disasterous results, perhaps even inadvertently aiding evil, or temporarily setting aside our honor for a geater cause, and ultimately undermining evil.
Of course, in this case I figure it'll work out for the better for the US and for Iraq's liberty no matter the intentions... but it may cost the Roman Catholic Church in the short run, and sooner or later, we- Protestants as well as Catholics, will have to address Islam in a unified fashion. I prefer that confrontation come later, in a setting of ideological debate and peaceful persuasion between free Men, instead of on the battlefield. Al Qaeda and Hussein would prefer that no such freedom to debate exists.