I think Ron Paul's comment about Chris Kyle and living and dying by the sword is a great new litmus test. Those who are outraged by it are not libertarians, are not against the warfare state, are not against the U.S. empire, and are neither friends nor fellow travelers of the liberty movement.
Update: Some have said that while they disagree with U.S. foreign policy, it is going to far to call soldiers killers and murderers. On the one hand, I never said that. I said you reap what you sow. Ron Paul said if you live by the sword you die by the sword. Someone is putting words in my mouth. But on the other hand, what do you call U.S. soldiers who kill in unjust wars? What would we call foreigners who came over here and killed our families while they were trying to free us from our oppressive government?