Yes, there is definitely always a difference of what you can do and what you think morally accepted to do. Realistically, I do not think 1147 archers would all shoot at the same time against a single unit, just as I do not think you'd think it right to let your people starve to gain a military advantage... unless you're Stalin or Mao.
Well removing food of regions that are being TO'd to starve an enemy has been done since it was possible I think, but you can certainly question the ethics of such decisions. And Garas has become a monster in terms of what he'll do for victory, which given how his story line evolved and what was done to him makes absolute sense. If starving 5000 peasants meant he'd gain a good victory, he'd do it in a heart beat.
Now on the matter of 1147 archers firing on a single unit, you can wonder how realistic it is, but it was an intentional game mechanic. If we want it more realistic we should add a feature request to allow some more complexity into the matter if that's at all possible code wise. And this does work two ways, as both sides can utilize the tactic. The big downside is however that the volunteer to take on the arrows is always wounded, if not killed.
There are also two distinct differences, what do you as a player see as morally accepted in terms of working within the game mechanics and what does your character view as acceptable. I can assure you that some in the south have been fighting Garas' more brutal ideas and plans, claiming it lacks honor. So that definately exists on a character level.
