Most of the crime in western states is centred around the "sink estates" (I guess you'd say the "projects" or ghettoes or slums). Would you advocate a huge police drop on these places, rounding up everyone and putting them in prison camps, to ensure you get the bad guys? I mean, where does one draw the line at these draconian measures? Wait a minute - Draco was just your apprentice!
Poor analogy - our government prosecutes those who commit crimes. When was the last time you heard Ahmadinejad seeking out a terrorist network in his own country???