"hideous ideologies" whose sole aim is to kill
It is wildly simplistic to say that terrorists' sole aim is to kill. It is much closer to the truth to say that their sole aim is to appear on television.
Acts of terrorism are performed to raise the profile of a cause, and especially to maximize media exposure so as to further the atmosphere of fear. Their goal is to influence an audience by causing fear amongst it, and killing is just a way of achieving that. "Performed" is the right word to use, because they are public performances.
Media coverage is a key incentive for terrorist acts, since mass media provides a reach across the whole population which a random act of violence in itself could not. The sad thing is that by providing days of wall to wall coverage on par with a Royal Marriage, some of the mass media are making it happen.