I'd like to focus a bit on the broader question of when speech during wartime is harmful to the war effort -- not necessarily when it's immoral, but only when it harms the war effort. To do this, let's first shift the discussion from the war on Iraq to World War II.
What speech (if any) by Americans during World War II do you think would have been harmful to the war effort, even if it weren't deliberately aimed at helping the Nazis win? If you think some such speech would have been harmful to the war effort then, but are skeptical about similar claims related to speech related to the war in Iraq now (as many commenters on this thread seem to be), why do you think there's a difference? (I should stress that I don't think that all antiwar speech is harmful to the war effort, and -- as I noted below -- that I don't think that even antiwar speech that harms the war effort is necessarily immoral. I do think, though, that a considerable amount of such antiwar speech is indeed harmful, and that people sometimes underestimate these harms.)