In the New Republic, Jonathan Chait exhorts liberals to get over their hatred of President Bush and support the war (which is very credible, considering the source):

As American liberals contemplate the current president's proposed war with Iraq, it's worth pondering his predecessor's logic. For if you accept Clinton's reasoning--and few liberals objected at the time--you can hardly help but resolve that we must eliminate Iraq's nonconventional arsenal by any means at our disposal, including, if all else fails, war. Two things have changed since Clinton's comments: First, in late 1998 Saddam effectively shut down U.N. weapons inspectors in Iraq, breaking the back of the already ailing inspections regime and granting himself four largely unfettered years in which to continue developing weapons of mass destruction; and second, in early 2001 Clinton was replaced in office by a Republican. The first of these points unquestionably strengthens the case for war: Saddam has provided strong evidence that he will not allow anything to deter him from pursuing weapons of mass destruction.
But many of my fellow liberals appear driven more by the second point. When asked about war, they typically offer the following propositions: President Bush has cynically timed the debate to bolster Republican chances in the November elections, he has pursued his Iraq policy with an arrogant disregard for the views of Congress and the public, and his rationales for military action have been contradictory and in some cases false. I happen to believe all these criticisms are true (although the first is hard to prove) and that they add more evidence to what is already a damning indictment of the Bush presidency. But these are objections to the way Bush has carried out his Iraq policy rather than to the policy itself. (If Bush were to employ such dishonest tactics on behalf of, say, universal health care, that wouldn't make the policy a bad idea.) Ultimately the central question is: Does war with Iraq promote liberal foreign policy principles? The answer is yes, it does.
...Deluded by the hope that they can have multilateralism and disarmament without the risk of war, liberals have concentrated their intellectual energies on the slim possibility that the United Nations will approve an airtight inspections system and that Saddam will submit to it. If that happens, they would not support a unilateral Bush war. And for that matter, neither would I. But the chance of that happening is small. We have eleven years of accumulated evidence suggesting that the United Nations will not approve loophole-free inspections and that even if it does, Saddam will defy it once more. Which is why it's strange to find so many liberals who consider themselves antiwar conceding that, if all else fails, they would support military action against Iraq. "All else" has failed for more than a decade. And barring a profound character reversal by Saddam, "all else" will likely fail again in the coming months. Just how many times are we supposed to go down this road before we realize our last resort may be our only option?

In the same issue, Robert Kaplan argues that Saddam is worse than Slobodan Milosevic, and that those who supported the interventions of the 90s on humanitarian grounds have no business objecting to the proposed invasion of Iraq:

Saddam is not just another dictator with whom we have to live. On a moral plane, even by the dismal standards of the Middle East, he is sui generis. The degree of repression is so severe in Iraq that whenever I would journey from Saddam's Iraq to Hafez al-Assad's Syria in the 1980s, it was like coming up for liberal humanist air. In Syria, despite the repression and the personality cult, you heard grumbling about the regime and could travel freely about the country, talking easily with people. Iraq was like the vast exercise yard of a penitentiary lit by high-wattage lamps, in the sense that nobody whispered a political complaint, and police permission was required to travel from one town to the next.
After I had my passport taken away from me for ten days by the Iraqi security police in 1986, an American diplomat in Baghdad told me that Iraq's was the most cowed population in the Arab world, and if the security services get it into their heads that you are suspicious, there is nothing anybody can do for you. Three years earlier, an American technician for Baghdad's Novotel hotel, Robert Spurling, had been taken away from his wife and daughters at Saddam International Airport and tortured for four months with electric shock, brass knuckles, and wooden bludgeons. His toes were crushed and his toenails ripped out. He was kept in solitary confinement on a starvation diet. Finally, American diplomats won his release. Multiply his story by thousands, and you will have an idea what Iraq is like to this day--at least, that is, until a Western leader has the gumption to stop it.
The only sensible comparisons with Saddam are Joseph Stalin, Romania's Nicolae Ceausescu, and Ethiopia's Communist tyrant Mengistu Haile Mariam, whose forced collectivization program in the '80s led to the deaths of hundreds of thousands in addition to the million or so who died of famine. Milosevic may be a war criminal, but his dictatorship was in many respects a subtle one that allowed for open power struggles and even for party politics and street protests. Milosevic did his share of political killing, but retaining his hold on power was often a matter of bribing and manipulating his political adversaries. Saddam only kills.
...Reagan's decision to deploy the nuclear missiles--a turning point in the cold war--could not by itself be defended by any universal morality, but it had a vast and profound moral result. The same will be true of an invasion of Iraq, just as it was of our invasion of Afghanistan. Make no mistake: This is a Reaganesque moment. For years intellectuals have pined for simple and consistent moral leadership on life-or-death foreign policy issues, leadership that does not cleverly parse words or twist and turn in the winds of politics and opinion polls for the sake of a tactical career advantage. Well, now they've got it. All of them, not just the neoconservatives, should support President George W. Bush's and Prime Minister Tony Blair's proposed humanitarian intervention in Iraq.

More notably, the Economist defends Israel against those who would equate its "defiance" of UN resolutions with that of Iraq. Of course, the article does not harp too heavily on the obvious points that Israel is neither run by a bloodthirsty dictator nor a pathological menace to its neighbors. But this is the Economist we're talking about here.) Perhaps they're trying to improve.