History is written by the victors, although he was a horrible man, consider this if you were Japanese during the bombings, what would you opinion be of Americans?
Well, I'd probably think of them as heartless monsters, but, had I the same personality as I do in real life, I'd consider which side the Japanese were on in the war, you know, I'm a rationalist, I take a look at both sides, and one of my mottoes is, "At some point, you'll have to do something you really, really don't want to," so I'm not too quick to judge based on actions such as bombings (Though I saw no good reason for 9/11), as they are usually reserved as last resort-type actions.
Now, with Osama, he worshiped Islam and was in Afghanistan during their fight to repel a Soviet invasion, where they had succeeded in driving off the Soviets, but then, he got carried away, and formed or joined a radical group known as Al Qaeda in which extremist Muslims join in hopes of gaining favor of Allah, which many Muslims in the Middle East, especially the younger ones, who are easier to manipulate, join, and kill all non-believers in the name of Allah.
Synopsis: Osama, or Usama, bin Laden is following one of the older, should I say, more forgotten or less practiced, rules of the Qu'ran, to kill or punish all non-believers, taking that rule, and using it as a basis for war, along with the rest of Al Qaeda.
My Personal Opinion: He deserved to die, his existence by itself was a threat to the US, the Middle East, and perhaps the world. Though there are others like him, ending Osama brings us one step closer to victory in the war on terror.