Who are the security people working for if everyone is a potential threat? If they managed to eliminate all of us "potential threats", there would be only security personnel on the streets, and that gives you an idea of who they are. With total power, they become a society unto themselves who work to preserve their own existence. Considering society as an organism, a security force with no accountability and absolute power is a cancer.
Mokalus of Borg
PS - Most anti-terrorism laws set up law enforcement with near-absolute power and limited accountability.
PPS - This does not account for distrust within the security organisation.