Some of them are 9-11 truthers who believe that 9-11 was a US government attack on ourselves.
As this article states, Ron Paul is closely affiliated with Rothbard. The Rothbard wing of the libertarian movement (Lew Rockwell, etc) believes that war is the instrument used by governments to expand their powers. The weak version of this argument is that governments only exploit a state of war to expand their powers. The strong argument is that all wars are insitigated by states to expand their powers. This is the basis of Ron Paul’s opposition to war. All else is a convienient figleaf.
The strong argument is why so many think that 9-11 was an inside job.