When Kirk wants to give guns to the primitive tribe so they can fight the other tribe on even ground because the Klingons armed the other tribe with muskets and gunpowder, Kirk has a reasonable explanation why he is doing what he is doing. At the same time the leader of the tribe is hesitant to accept the guns because of his pacifist beliefs and McCoy is against Kirks plan because he thinks it will lead to more lethal and violent war between the tribes. All parties have a legitimate argument to what's going on and all three are right in their arguments. At the end of the day the episode ends on a bittersweet note where Kirk realizes what Starfleet and the Klingons interference has done to the planet and concludes they were serpents in Eden, they both brought their warlike ways to this planet and the only realistic scenario is to arm both sides with guns knowing they will go to war with each other.