Most people would think that reasons to avoid war would be obvious to anyone, but I think this reason is very damning to our current war efforts. The New York Times had an article about various murder cases related to the war in Iraq.
Later in the article it discusses a case where an Iraqi civilian was killed by American military personnel. This doesn't sound strange considering it is a war, but this is what caught my eye:
As part of the plea agreement, Private Jodka testified that he participated in a plan formed by the squad leader, Sgt. Lawrence G. Hutchins, to kidnap and kill a known insurgent. In the dark, the squad kidnapped and killed the wrong man.
This is a perfect example of military personnel doing something wrong which they justify as being right in the name of war. I am not talking about the mistake of getting the wrong man in the dark. I am talking about the plot to abduct and kill a terrorist. If it had been a legitimate operation they would have been planning to capture and interrogate the terrorist. In that case, getting the wrong man would have meant that they could free him.
Why this is a good reason not to go to war is that anytime we go to war we set the stage for these kinds of "operations" orchestrated by men like Sgt. Hutchins (who appears to deserve the bulk of the blame here).