If it proves true that one or more Marines acted in a clearly improper fashion,I think it's more likely due to the stresses of war.Add to that the likely fact that the 9th Century knuckledraggers are doing their best to maximize "the fog of war" and,thus,civilian deaths for propaganda proposes and you've got a bad situation,image-wise.
Operative word was "possibility."
Would hate to see them saying as Harry did: "Remember us, lad! Scapegoats of the bloody empire!"
BTW: The BEST line is: A slice off a cut loaf wont be missed."