Bad OT Justifications for War

In talking with people about the Iraq war who trot out God's violence in the OT as God's support of violence and subsequently (obviously!) the war on terror, I have just one observation:

If the appealed to picture of war in the Old Testament is God-ordained holy war (which it is), and if the war against terror is to defeat the holy war of Militant/Jihadist/Radical Islam, then it makes no moral sense to appeal to the holy war of Israel as God's support of violence against another form of holy war. We cannot critique the Jihadist and appeal to our own holy war without cutting off the branch of the tree we're sitting in. Please find a better appeal.