If you want to look into it even further, even the Bush Jr. admin's wild goose chase after weapons of mass destruction can be seen as mass paranoia on a national scale. It's important to recognize these signs of successful psychological warfare so that we can build societies that are less susceptible to it.
The Iranian revolution is another example of a very successful terrorist propaganda campaign that managed to completely destabilize what was a modern country with an intelligent, secular population. Don't think we are immune to contracting such sickness, that would be very naive.
Remember the famous experiment where regular people were put in a facility and given roles of prisoners and jailors, and how they gradually descended into violence and martial law on their own. There was a counter-experiment in which a planted individual was directed to point out this insanity and act in a humane way to the would-be-prisoners, and once the other jailors saw his example, they went back to behaving rationally and the aggression was averted.
The conclusion is that minds are susceptible, just like bodies are susceptible. And the treatment for sick, violent thinking is healthy, rational thinking.
