It is very easy to identify the enemy: The enemy shoots at you.
Not in the fight against terrorists. It could be a guy on a bus with an explosive vest. By your logic, no action should be taken until the guy detonates.
I am not trying to be glib. The West, the USA in particular, is in a fight against non-state enemies. These people do not have uniforms, government, or even a united agenda. For all the press that Bin Laden gets, he is not in operational control. No one is.
Regarding peace without fighting, I am open to ideas. I have thought about what would get the terrorists to stop. The only scenario that I can come up with is something like pre-war Iraq or Afghanistan. Neither was a paradise. From their citizens perspective, were they better? For some, yes. For most, I don't believe so.
Regarding the video, I haven't seen it. It seems a decision was made on the spot that is now getting second guessed.