What you have to do is to chose the least worse solution.
So instead of violating a smaller number of peoples rights the US chose to violate everybody's rights with the TSA and the NSA. Even us who is not even living in the US or plan to go there.
The defenders then try to hide behind it with the argument that is fair, because everybody is mistreated. No it isn't. Violating several millions people is far worse than a few thousands. Especially violating peoples rights that can't even remotely be classified as a US person, like me.
And what was the end result of this nonsense US policy? Boston bombings.
Why? Because if you make everyone a suspect that is the same as saying there is no suspects.
In all of these cases, there where signs, but officials chose to ignore them because it is politically incorrect to profile on suspicious behavior and appearance.