The libertarian criticism of the GWOT is a criticism on how much the state expanded under Bush, and the mistakes made in our name in Afghanistan, Iraq and Gitmo
I supported the Iraq War, and would do it over again if asked. I think there needs to be an aggressive foreign policy on our part
However, the amount of money that has been spent, along with the absurd expansion of the state since 2001, not to mention that reducing entitlements (medicare, medicaid and SSI) along with the military is the only way to reduce our national debt long term.
Essentially the argument is that the GWOT has wasted money and expanded government, things libertarians oppose, and conservatives used to oppose
An unending "war on terror" in which we hold hands with the nations who provide ideological and financial support to those who want to kill us is NOT acceptable and I see no reason to support that.