Trying to restate the parts of this topic that I agree with.
Terrorism is a tactic, a way of achieving your goals. You can consider a heinous way of doing so, or you can call it the resort of those with unworthy goals, or a ineffective way. But nonetheless it is a deliberate method of trying to effect change.
Terrorism is not a defined enemy. A "War on Terrorism" makes about as much sense as a "war on ambushes", a "war on frying-pans" or "war on drugs". It may be useful as a rhetorical device and a power play, but it is not clearly defined in any meaningful or legal sense. And it can't ever be decisively won, since anyone can use the terror tactics, and there is no single enemy leader that can capitulate.
If war is the extension of diplomacy by other means, then terror is the extension of war by other means. An organisation that can't compete head-on against a large military force can still afford the apparatus of a few bombs, guns and martyrs.
It is not tenable to say that conventional war (whatever that is these days) with all its attendant tactics, can sometimes be justified; but terror is always bad. What is the distance from Terror to Shock and Awe? Dead is dead, and although terror has as civilians the primary targets and war has them only as collateral damage, the facts remain that in the so-called "war on terror" more innocents in the third world have died, terrified, bombed, than in the first world.
It isn't valid to claim that any organisation that uses terror has invalid goals. The ANC employed a terror campaign in the mid 1980s, and P.W. Botha was fond of calling them "communist terrorist insurgents". By the mid 1990s we were calling them "the government". This was a positive change. Irgun used terror tactics to promote Israeli independence.
It isn't valid to claim that the use of terror invalidates the goals of the user. Not unless you also want to invalidate any user of military bombardment too, and then exist in a world consisting only of blackened pots and darkened kettles, accusing all and solving nothing. Long-distance bombardment is just as one-sided, and just as terrible. War is hell. Terror is a part of this.
Terrorism is a tool of war, sometimes the last weapon left to the dispossessed and desperate. Is playing to your strengths only a good thing if your strength is having an army? Understanding the reasons for what happens is better then trying to pass them off as intrinsically evil.
How to fight terror? Like the man said, You want peace, you must work for justice. Empty, self-serving rhetoric about democracy and freedom, whilst occupying countries where the majority want the occupier to leave, and suggesting that the third world become like the first, when the first world's position is a consequence of there being a third world, is not just.
By all means, declare a legally constituted police action or international enforcement against specifically identified drug cartels or terror-using extremist organisations and individuals. But open-ended campaigns of general enforcement are part of the problem, not the solution.
Current organisations that employ terror can be examined on the basis of their goals, and some of them will be found to have radical, luddite, intolerant and impractical goals. But they will still attract support as long as there is injustice.
"A terrorist is someone who has a bomb but doesn't have an air force"