Ok, I have access for a little while, so here's a longer piece.
Atrios wrote a very insightful piece yesterday about the problem with many liberals that supported the invasion of Iraq- that despite the clear reality that there were no weapons of mass destruction or indication that it'd accomplish any of its goals, those who opposed it at the time are marginalized. Not were, are. Atrios (echoing Tim Noah) considers that insane. Atrios described it as a liberal "testosterone test". Some people got mad at him, largely liberal hawks like ogged who are pissed at Atrios "hounding liberals who supported the war", but he's more right than wrong. Another, Jack O'Toole, asks "does [Atrios] really believe that people like me -- people who've spent our lives fighting for the same progressive ideals that he holds dear -- could possibly think that way?"
Atrios drew the distinction. I don't. Sorry, ogged and O'Toole, but your attitudes weren't part of the problem, they WERE the problem.
The key issue, however, isn't Iraq and never was. The problem is unity and division. I've brought this up many times, but the key strength of the right and key weakness of the left is that the right gets to define all the issues, and thus remains publicly united when it comes to dealing with both domestic and foreign policy issues. People on the right disagree, but they agree to table their disagreements when dealing with the "other guy"... the liberals and the left. Part of this is due to the visceral loathing that most have for both the liberal left, but it goes further than that, and it gets back to liberal hawks.
Many (if not practically all) Liberal hawks (along with "centrist" liberals) are naturally focused on legitimacy. They want to be part of the discussion, but it's a discussion that the right has framed. They are, further, either unwilling to change that framing, or are ignorant that it is even taking place. Thus, in order to gain legitimacy, they need to accept the framing concepts that the right has built up. This means that they're essentially doomed, of course, because they're fighting on foreign terrain... but if you see this as a choice between relevance or irrelevance, then anybody sane would choose the former, right?
Unfortunately for them, the right has little interest in actually dialoguing with them. What they provide is legitimacy for the right's arguments... the classic "even the liberal [insert name here]" argument that we're all familiar with. It's the classic intelligence concept of "grey (or black) propaganda"... you know that your opponents aren't going to listen to you, so you get some that is presumably "neutral" or even "opposed" to make your arguments for you. It works spectacularly well, as we've all seen, especially when they're doing it of their own free will. They are quoted and used to the extent that this role is necessary, then are thrown away. Of course, they're all familiar with this too, but the argument remains... isn't it better to be relevant?
The weapon that they provide, however, is aimed squarely at those who could actually change the framework of the debate. There are, naturally, a lot of people on both the liberal and radical left who don't accept the framework, and attempt to break out of it. The radicals pretty much exist entirely for this purpose... it is their raison d'etre, and whatever disagreements that liberals have with them, it's an important role. (Yes, this includes the protest movement.) Even relatively "normal" liberals, however, often question a lot of the conventional wisdom and accepted assumptions that provide the framework of debates. Were the left in the United States akin to the right (or, for that matter, the left in, say, Canada... the situation is quite a bit different there), this would mean a tug of war between framers on the left and framers on the right, with the actual debate being held somewhere in between. This is where that legitimacy becomes critical for the American right, however, because they use those liberal hawks to ensure their framing assumptions are dominant. The same does not exist on the left, because the right simply doesn't have the same numbers or kinds of legitimacy-granting "opponents".
The practical upshot? The right (nominally the Republicans, but of course it's bigger than that) depended on their "Saddam was going to build WMDs and ruin the region" story to support the invasion, and by selectively choosing which liberals to praise by making the "proper" arguments for a "proper" dialogue, they ensured that those on the left who depend on access and acceptance by their rivals on the right will grant the legitimacy they need and force out those who are looking at the situation through a different set of assumptions. They knew that arguments by self-named "liberals" would carry much greater weight as classic grey (or, perhaps, black) propaganda. They put the machine into motion, the usual suspects came through for them, and everything seemed to be going swimmingly until they had the error of their assumption shoved brutally in their faces.
This creates a problem for the right, but they still control the frame. It creates a much BIGGER problem for liberal hawks, because the one source of power they have-- legitimacy-- is utterly threatened. Thus we get to where we are, where we end up with the bizarre situation where you can't be taken "seriously" unless you made a massive mistake. The fundamental problem of the left cannibalizing itself remains, and as long as it does, this sort of DoubleThink isn't going anywhere.
Fortunately, the solution is simple, and somewhat embodied in something O'Toole said. He said "When demagogues like Andrew Sullivan challenge the motives (i.e., the patriotism) of the liberal wing of the Democratic party, I stand shoulder to shoulder with my friends". It's a good start, but it doesn't go far enough. What liberals (not merely Democrats) need to do is accept that trying to leech acceptability from those who are opposed to everything you stand for is a mug's game. You're being used and thrown away. When somebody like Scott Ritter comes up and says "I was right, and you didn't believe me", the general liberal response should be and must be "you were right, we were wrong, we apologize to those whom we so thoroughly denigrated before the war and pledge to put away the right's convenient filters and listen to you in the future". Then, when the time comes, somebody other than Paul Krugman needs to speak up and say "these people have a point, they're not 'un-American', and we'll stand up for them and pay close attention to what they have to say, no matter what kind of flak we get."
Just stop being tools. It doesn't mean you have to agree with ANSWER or whatever, but stop being tools. It's demeaning, and it's why liberals continue to struggle.
Edit: One other thing. O'Toole said that cheap shots should be left to people like the RNC. No. Wrong. Utterly wrong. This "holier than thou" attitude is one of the best GreyProp weapons out there, because its melding with liberal equivocation lends even the most scurrilous attack credibility by being even dimly associated with those who "behave better". ("Sure, Rush said some horrible stuff, but this other liberal guy said something like it, and he's a LIBERAL and above this sort of thing. Maybe Rush is just 'overstating' an essential truth, and those who are attacking him are just covering their asses.")
If you're a centrist liberal who has been playing the legitimacy game, then you're hurting people you should be helping. Period. Take your medicine and start laying off the "own goals".