Gary Gutting wrote for the new york times:
A similar dilemma undermines the revolutionary tendencies of the far left. They must either deny the obvious fact that protecting Americans from terrorist attacks requires a substantial government surveillance system or they must agree that the only debate should be about how this surveillance system should work, not whether it should exist. Taking the second approach means accepting the fundamental legitimacy of Obama’s anti-terrorism program and merely challenging specific aspects of this program.
How is it an obvious fact that protecting Americans from terrorist attacks requires a substantial government surveillance system? This aggrandizement of our intelligence community baffles me. In most walks of life, you have to prove your worth. Only in security can they say, "Well you don't see any dragons breathing fire down your neck, do you? You're welcome."
Indeed, the whole surveillance complex depends on there being a target to observe. Like any living organism, it keeps growing at everyone else's expense. We do not want another J Edgar Hoover but if we have a massive surveillance state, no matter how pure the objectives are, sooner or later we will have a Hoover in charge of it. There will be no survivors.
If you needed any refresher on how horrible a man Hoover was, here is an excerpt:
According to President Harry S Truman, Hoover transformed the FBI into his private secret police force; Truman stated that "we want no Gestapo or secret police. FBI is tending in that direction. They are dabbling in sex-life scandals and plain blackmail. J. Edgar Hoover would give his right eye to take over, and all congressmen and senators are afraid of him".
 from Wikipedia quoting Anthony Summers, "The secret life of J Edgar Hoover", The Guardian, Sunday January 1 2012 https://en.wikipedia.org/wiki/J._Edgar_Hoover