His reasoning is interesting - no, it's not WMD, nor lack of international support, he hasn't based this on the deaths of our soldiers and Iraqi civilians (which combined make enough of a reason). He goes beyond that:
Why we Have to get the Troops Out of Iraq
The hundreds of thousands of protesters who came out throughout the world on Saturday were demanding a US and British withdrawal from Iraq.
The protesters are right that we have to get US ground troops out of Iraq.
--snip---
The first reason to get the ground troops out now is that they are being fatally brutalized by their own treatment of Iraqi prisoners. Abu Ghraib was horrific, and we who are not in Congress or the Department of Defense have still only seen a fraction of the photographs of it that exist.
We as a nation are losing our soul, our greatness, and are falling into a pit of evil and depravity. How could we send our sons and daughters to carry out this insane behavior at our behest?
---snip----
The second reason is that the ground troops are not accomplishing the mission given them, and are making things worse rather than better.
Prof. Cole goes into great detail describing the politics of Iraq, and, trust me, we've made it worse, big time. The way he describes it reminds me of a blender turned on "high".
----snip-----
I conclude that the presence of the US ground troops is making things worse, not better.
Let's get them out, now, before they destroy any more cities, create any more hundreds of thousands of internally displaced persons, provoke any more ethnic hatreds by installing Shiite police in Fallujah or Kurdish troops in Turkmen Tal Afar. They are sowing a vast whirlwind, a desert sandstorm of Martian proportions, which future generations of Americans and Iraqis will reap.
The ground troops must come out. Now. For the good of Iraq. For the good of America.
This man knows - he's followed it more closely than most.