Due diligence...of course. But I don't believe in this administration's excesses. The ad hoc suspension of the Constitution, the trampling of civil liberties, the "antipatriotic" labeling of anyone who questions or criticizes the means to the ends, the ending of careers as punishment for not falling in lock-step behind this administration, the parallel government run from the vice-president's office....etc., etc.
If the goal of the terrorists is to bring down our form of government because they hate freedom, maybe they've come closer to winning than we want to admit?
In response to your question, we have of course done what was necessary to protect ourselves. But not EVERY step we've taken was necessary. I am in firm belief that some actions were absolutely right, some were absolutely a mistake, some were opportunistic, some were illegal, some were out of fear, and some were pure ego.