I'm not sure that I understand your argument. War consisted of making life or death decisions based on insufficient information both before and after the Geneva conventions.

Of course on the battlefield incorrect decisions must be made. However, drone strikes like the Afghan farmers do not fit that criteria. The decision did not /have/ to be made. It was a voluntary assassination.

When did the Taliban sign on to Geneva?

Not only does your logic bending (to for some reason avoid the basis of wartime morality?) fail in its own premise as the Taliban is not allowed to meet your standard as they are not a sovereign nation able to be a signatory, the convention itself does not work as you imply:

"this Protocol must be fully applied in all circumstances to all persons who are protected by those instruments, without any adverse distinction based on the nature or origin of the armed conflict"

Random Afghani civilians are not the Taliban.

(Aside from the fact that the Geneva Convention doesn't work that way, as the other guy pointed out.)