Well, just for starters...
The people hung from the bridge, after being dragged through the streets and burned, were civilian contractors who had been driving a vehicle through the town when they were attacked by small arms fire and rocket-propelled grenades. The attackers were in absolutely no danger from these contractors.
The man shot by the Marine was an insurgent who had, the day before, been shooting at Marines from inside a mosque, in an environment where booby-trapped corpses and insurgents faking death were already routine occurences, and in fact a booby-trapped corpse had killed a Marine from that same unit the day before.
See any difference at all?