Your comment presents a false dichotomy between the particular responses they took and doing nothing.
It ignores the possibilities of other courses of action, by implying that if the particular responses they took were poor then the best option therefore must be to do nothing.
BTW. GP forgot to add - terrorizing Pakistan. US drone strikes themselves killed about as many civilians as 9/11 attacks.
I dispute your claim that every possible option other than doing nothing would be worse than doing nothing. What's your justification for that claim?
Now sure, some people will look at pages of facts and figures about death statistics. But a lot of people will think "I had to wait in line for a long time at the airport while they did security stuff, so I must be safe." And that's the job of government, to deal with problems that are on the minds of citizens.
When "doing something" is worse than "doing nothing", then yes we should do nothing. Off the top of my head, the things we've done because of 9/11:
* Create DHS
* Begin TSA security theater
* Start illegal NSA metadata collection program
* Afghanistan + Iraq ("not related", but had support from misinformed public) wars.
A good thing I can think of: more secure cockpit doors. On balance, yeah, I wish we had done nothing after 9/11. On the other hand it's not impossible for good actions as a result, but we have a pretty bad track record of it.
The importance of putting the _actual_ consequences in perspective is to let you at least consider that maybe we don't have to do anything sometimes. It's like the 80/20 rule or anything with diminishing marginal returns: to actually achieve flat out 100% safety and security is going to be an extremely expensive endeavor both in monetary terms and in how our society and ideals have to change.