If we substitute the name Charles Manson for Bin Laden - the descriptive word changes from morals to insanity. IMO - the two are very similar in that they both convinced other people to blindly do their killing.
Is it insanely right to kill him?
Sorry think I've missed the point of this.
If he is 'insane', it doesn't change things. There's still a question of "is it morally right" and you still need to choose a moral basis (whether your own or someone elses).