The marginalization of pessimism on Iraq, not just by right wing hacks and pundits but by mainstream journalism has always inhibited conversation on the subject. You're simply not allowed to do anything but clap louder.
I know there were a couple more examples of this but I've only managed to find one so far. When Dean made his "gaffe" that capturing Saddam Hussein didn't make the country any safer a few Washington types expressed a version of "he's absolutely right but he still shouldn't have said it because we're going to attack him for it anyway!" I give you Sam Donaldson:
DONALDSON: Let me tell you something. I think Howard Dean deserves the bad press. And I'm not against him. I'm not making a case against him.
That one phase, "America is not safer because of Saddam's capture," in context you know what he's saying, which is the war on terrorism is a wide-ranging war in the future and this will not really affect that. But someone on his staff should have said, "Don't use that phrase because every headline and writer, every Donaldson, everybody on television will stick it out, and it's just the wrong message.