While they are both being dumb doing this when enemy soldiers are around, the MC is being worse. A soldier picked that job for some reason and signed themselves for whatever fate the conflict brings them. So when they want genocidal powers you don't get to say "maybe we compromise", you make a decision to either stop the threat or allow the threat to continue. If you stop the threat first with diplomacy that's fine but the MC chose defense, then the only way to stop the threat is to destroy the enemy