9/11 happened, and this policy was formulated, which resulted in a complete change of the policy towards Iraq.
Note that it also resulted in a change of policy towards Iran, Syria, Libya, and North Korea...none of which anyone pays attention to. If people would, then how the administration formulates policy would be much clearer...which is the real argument here. Changing our foreign policy after 9/11 was not being weaselly...far from it, it was as logical a step as Roosevelt abandoning the trappings of his faux-isolationist policy after Pearl Harbor. The drastic change of policy across extraordinary events isn't inconsistent...it's natural, even necessary.
This administration, however, has never been one to support Constitutional protections or separation of powers, before or after 9/11, except when such Constitutional powers suited it. On that single matter alone - failing to uphold his oath of office to defend the Constitution - I would have voted against Bush in 2004...except that Kerry's record on Constitutional matters was actually worse.