[adamors]

Not just Hitler. Naomi Klein (of No Logo fame) wrote an excellent book about it, called The Shock Doctrine [1]. She lists numerous examples in the last 50 or so years how convenient, but shocking events were used as excuses to implement controversial laws, that often either limited freedoms or made the life of people more miserable.

She mostly approaches the issues from an economical perspective, mainly focusing on inhumane economic policies that both Thatcher and Reagan implemented, but the gist is similar.

[1]: http://en.wikipedia.org/wiki/The_Shock_Doctrine

[hackuser]

Generally Congress does not act until there is an overwhelming impetus to push them over the threshold: They have limited time to deal with the whole nation's and world's problems; and they are responsive to a body, the public, which is uninformed, has a short attention span, and is highly reactive and rarely proactive.

Therefore it is not surprising that shocking events lead to controversial laws. Shocking events arguably lead to most laws; it's hard to get something done unless something shocking gets the public's (and members of congress') attention and causes a reaction.

Of course, people in power are aware of this phenomenon and plan their tactics to take advantage of it. I remember reading that many provisions of the Patriot Act were written long before 9/11 and its authors had been awaiting an opportunity. Or as the Obama administration said early in its tenure (IIRC), 'never waste a crisis'.