What Glenn says: the oath our President takes is to protect and defend the Constitution, not to keep the Homeland safe.
But that's the central choice the Founders made: that there are more important values than maximizing safety. If they didn't think that way, they would never have risked fighting the most powerful military on earth -- all for some abstract political liberty. By itself, that choice reflects the view that there are more important goals then keeping us safe. Tyrannies might be the best guardians of national security (though it is highly dubious that indefinitely locking up Muslims with no trial and no charges will Keep Us Safe), but either way: the U.S. wasn't created to be a National Security State.