They seem to be under the impression that everything or everyone is against them, and exaggerate the effects of policies conducted by an organization that they do not like.
For example, Libertarians are adamant that Quantitative Easing is vastly different that other monetary policies conducted by a central bank. It wasn't simply 'printing money' as they would like to believe; it operated as an asset exchange, like other monetary policies. The reality was that inflation was minimal. Ultimately, QE didn't work as intended. I'm not suggesting it was 'good'; I'm merely pointing out that Libertarians seem to think that there will be massive consequences from any given action.
The effects of min. wage are also HUGELY overstated. To them, a small increase in the min. wage is going to cause rampant inflation & unemployment.
Their distrust in the Federal Reserve ultimately clouds their perception of reality; they frequently suggest that the Fed should be audited by an independent organization....and that it's not right that it isn't....but wait, it is- at least in most aspects (there are some areas where it isn't audited, but Libertarians seem to be under the impression that it isn't audited AT ALL)
Why are Libertarians such alarmists? They exaggerate the effects of practically everything....