I find the hardest thing in getting the "real level of morality" (read: the amount of distress caused to other beings) of an action is that one would have to wait until the end of time to be sure that all
"distressing reactions" regarding that action are taken into consideration. Everything else is just assumption about the morality of an action.
And, for instance, you could not simply consider killing Hitler a pretty moral action. Because killing him in December 1944 would be less moral than if he'd be killed by a drunken driver in a car accident as a young boy, what on the other hand might just increase chances that Russia takes over whole Europe, except if he dies one day later when he's been pushed down a cliff and he could tell someone about his plans to take on the world, who will now do it instead, with more success, btw.
Err, well Spider, lead me words ad absurdum already