He is not doing a direct comparison between WWII and GW volume II. He is providing a hypothetical situation to give some context to the revelations that happened shortly after the war began in Iraq. There were some problems with the intelligence that linked Iraq with 9/11. If 9/11 was the reason we went to war with Iraq, what if Iraq had nothing to do with 9/11? The historical backdrop is to illustrate how we might perceive things differently if we are to remove ourselves from the current situation. The point is "how would we have felt if we went to war with Japan over Perl Harbor if we found out they had nothing to do with it" and how is that somehow different from our situation with Iraq given that they might not have been involved in 9/11. There is no direct comparison between the Iraq war and WWI because the situation he presents with regards to WWII never happened.