Well that's why I originally said for this to work and for us to be free from our definition of terrorism we need to kill anyone who could be reasonably radicalised in the first place. So aside from nuking the middle east (and that sounds so simple) you'd also have to kill all the splinter cells in Africa, Asia, Europe and America plus anyone who follows the same values but in a more moderate manner (i.e. innocent Muslims if we're targeting Muslim terrorists who would almost certainly turn radical if such a thing were to happen).
I didn't say it was a good or a moral way of doing things, just that to stop terrorism you basically need to think like a terrorist. Dehumanise everyone and kill the ones that don't agree with our way of life. To them, we're the terrorists and they wouldn't think twice about killing us.
All it really highlights is that it's a thankless task for the intelligence services and the governments in charge of our societies because we're constantly under threat.
We will end up in an Orwellian dystopian society of surveillance where thought is prohibited just to make sure no attacks like this happen in the future. But even that will fall apart because there'll always be a resistance. We're humans and we like to argue. Arguments lead to fights, fights lead to wars, wars lead to oblivion.
