It may have been a short story but I remember it distinctly as being a poem. If it is a poem it is most definitely NOT Drummer Hodge or Drummer Boy of Shiloh.
A soldier in battle draws a bead on and kills the young drummer (piper?) of the opposing force. At some point he is questioned about his decision to kill an unarmed boy.
His response is that the one who rallies the soldiers to battle is at least as dangerous (and culpable) as the armed soldier.
I read this about 30 years ago in school (don’t recall if it was in a collection or a xeroxed hand-out.)
Any help would be appreciated as I want to read it to a child of mine who doesn’t grasp that the one who incites the riot is as guilty as the rioters.