I get your point, but I don't think this is necessarily that black and white. I've read plenty of quotes from Iraqis of the nature of "Thank you for liberating us from Saddam...now get the !@#$ out of our country." Even if you simplisticly boil the "liberator/invader" label down to "What do the Iraqis think?", it's not as clear as you make it out.
A lot of it, of course, depends on the nature of the poll as well. What question did the polled respond to? "Do you want the US out of your country?", or "Do you wish the US never entered your country?", or "Do wish the US never got rid of Hussein?", while roughly equivalent statements, will garner vastly different responses. It also matters, too, who you ask...is that 80% of everyone in Iraq, or 80% of Kurds, or 80% of Shi'ites, or 80% of Sunni Ba'athists? It's perfectly reasonable, I think, to question the nature of Dean's claim, as it's again NOT that black and white, and all polls are not created equal.