Please remember the lessons of history, and read or reread the story of the rise of Nazism, or of the "excuses" utilized immediately prior to one of the Soviet (or Communist Chinese) purges. Governments have always used the excuse of an "emergency" to significantly broaden their powers, and to claim the right to use "extraordinary" means. And those means are always justified by an appeal to "public safety," or an appeal to "saving the lives of our citizens," or something similar. It was precisely this kind of mentality that led to adoption of the first Patriot Act, which many of the lawmakers voting for it did not even bother to read, either in whole or in part. And we are still discovering the new government powers granted in that act -- and the same pattern will make another appearance in the wake of another domestic attack, you may be certain, and that may bring us Patriot Act II, containing a whole new host of government powers of which very few people will even be aware.Also, extensive Hannah Arendt quotes discussing the use of torture by the Nazis.
This is precisely how the road to a totalitarian government is followed; it has always been thus, and it always will be.
More Torture - Arthur Silber has a good blog post where he lays out the practical, and libertarian case against torture.