Earlier quoted context omitted.
Terrorism cannot be stopped (by definition). The affront to freedom is the response to terrorism.
What part of the definition says that it can't be stopped?
What does it take to create fear? Certainly not successful terrorist attacks. Failed ones would work perfectly well too, as evidenced by the underwear bomber, shoe bomber, etc.
Things as minor as prank phone calls, etc., will still strike fear into the hearts of the target population.
So unless you can tell me that it's possible to stop failed attacks and prank phone calls, you must agree that terrorism cannot ever be stopped.