The Federation was engaged in a Cold War type of competition with the Klingons - the comparison was specifically drawn. In "A Private Little War" Kirk sacrifices the local culture's values for the self-interest of the Federation.
I don't want to get in the way of the beatdown you're giving Cheapjack, but it's not quite clear that Kirk had any way to preserve the local culture in APLW even if he had wanted to. If the Klingons can destabilize the situation by giving advanced military techs to the townsfolk, then preserving the peaceful hill culture just isn't on.