Everyone is non-violent until they're not and there is a rational trade-off between civil liberty and security (the risk/reward balance ranges from the U.S. to Singapore to Stalin's Russia). There is a proper way to do this - peeking into suspects' lives for suspicious activity, and if nothing is found, to hide away the file. While most protesters in Benghazi weren't bad it created a predictably attractive environment for violence-biased individuals.

As a personal aside and a New Yorker, I've been concerned by the sometimes violent proclamations of OWS protesters (as well as thoroughly pleased by the coherence of a diminishing minority's arguments). I would be dismayed to the point of taking action if NYPD CT weren't monitoring the group (once an individual leaves the group the civil liberties side weighs in higher as a temporary phenomenon indicating an elevated risk profile has passed).