Bin Laden was not a king or a head of state.

He was a criminal considered armed and dangerous.

Unless he was stark naked when shot, the SEALs had every reason to suspect he could be wearing a suicide belt. Inside a fortified enemy compound with only one way out, faced with the most wanted fugitive on earth and an unknown number of his bodyguards, the only way to prevent shooting would have been for everybody but the SEALs to throw up their hands in surrender. Everybody.

Under the actual circumstances, it would have taken superhuman and possibly suicidal restraint not to shoot him. The fact that so few shots were fired, and that the U.S. government frankly admits Bin Laden wasn't holding a weapon (and is now debating whether the release of photos would be offensive) shows how America actually tries to operate.