He was not authorized use military force against Iraq in order to commit such an insane act by the AUMF vote in October 2002.
Of course he was, they left it completely to his discretion. Why else would they give him the unconditional authorization. If Congress intended to compel him into diplomacy as you are claiming, then they would have adopted the Spratt amendment which does compel him into diplomacy and also puts conditions on the use of the military.
SEC. 3. AUTHORIZATION TO USE FORCE IN ACCORDANCE WITH NEW UNITED
NATIONS SECURITY COUNCIL RESOLUTIONS.
The President is authorized to use United States Armed Forces
pursuant to any resolution of the United Nations Security
Council adopted after September 12, 2002, that provides for the
elimination of Iraq's weapons of mass destruction and ballistic
missiles with ranges exceeding 150 kilometers, and the means of
producing such weapons and missiles. Nothing in the preceding
sentence shall be construed to prevent or otherwise limit the
authority of the Armed Forces to use all appropriate force for
self defense and enforcement purposes.
SEC. 4. PRESIDENTIAL CERTIFICATIONS.
In the event that the United Nations Security Council does
not adopt a resolution as described in section 3, or in the
event that such a resolution is adopted but does not sanction
the use of force sufficient to compel Iraq's compliance, and if
the President determines that use of the United States Armed
Forces is necessary for such compliance, the President should
seek authorization from Congress to use military force to
compel such compliance by invoking the expedited procedures set
forth in section 5 after the President submits to the Speaker
of the House of Representatives and the President pro tempore
of the Senate a certification that--
H. Rept. 107-724 - PROVIDING FOR CONSIDERATION OF HOUSE JOINT RESOLUTION 114, AUTHORIZATION FOR USE OF MILITARY FORCE AGAINST IRAQ RESOLUTION OF 2002