[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'.