Granted OBL can't pull any more triggers, but I wasn't aware that was what made him dangerous. Somehow I can't believe that until OBL was killed, AQ members thought they were immortal—gives a whole new meaning to their oft-used 'martyr' terminology—so I can't see the slightest deterrent effect. Whether they're 'enemy combattants' or soldiers, when you join a war dying is one of the possibilities. And of course there's the other: that they get smarter, more resourceful and split up their leadership. Look up Hercules and the Hydra.
And I'll grant you your "unevolved", which is definitely one of the reasons we aren't doing much in the way of winning hearts and minds. They can see our words are empty.
Of course OBL was never going to directly kill anyone himself; it's not very becoming to be deliberately obtuse [a la Fuji].
If you can't see the slightest chance it is a deterrent then you should try to look with a more open mind. Obviously OBL wanted to live or he wouldn't have tried so hard to hide for so long and the same applies to the most other terrorists [a reasonable person would assume]. It will probably make anyone tempted to assist these fanatics a bit more reluctant given the US's demonstrated ability and determination to eliminate them whatever rock they hide under. Another probable benefit will be the extra care they will need to take to communicate to conceal their locations; this can only help slow down and interfere with their ability to plan and carry out atrocities.
As far as the risk that eliminating the leader will make them more dangerous overall, I will live with the miniscule chance that chopping off the head ends in a more dangerous organization. Another fable I don't believe in is that you can win these people over by treating them reasonably. I'd rather keep exterminating the worst and then see if the moderates and progressives can then be reasoned with. I hardly think the hardcore fundamentalists really listen to the Beatles and subscribe to their take on love that you quote.
In the end, the actual course of action will probably fall between my unevolved approach and your oh so civilized path. In the meantime I am just enjoying the glow from seeing the most notorious terrorist erradicated. It is a sweeter dish when served cold.
D.