There's been a report recently of a Rand Corporation study. It surveyed almost 650 terrorist groups that operated between 1968 and 2006. This is how they died:
43% ceased after a transition to the political process.
40% were destroyed by effective police work.
10% dissolved after victory.
And 7% were defeated militarily.
Note that - police work destroyed 40% of them, the military destroyed 7%. And this is the Rand Corporation saying this, not some leftist peace institute.
Feel free to cite these figures the next time wingnuts start getting erections over weapons.