Smart ass...
OK. From my view of things... there is no excuse for assassination. It is an evil action and the ends would only justify the means with hindsight.
One would not know in, say, 1928 that Hitler was going to be what he turned out to be. Killing him in 1943 would be an entirely different matter. If you follow me.
OBL doesn't need to be killed. He needs to be arrested. Besides, killing OBL isn't going to stop terrorism, is it?