Yeah, his negotiation skills leave something to be desired. If you force others to fight by holding hostages, they won't give their 100% effort and the topmost thing on their minds is how to get rid of you first, not the enemy you are trying to make them fight. It's especially more so with those with actually usable fighting ability.
This feels more like Woo-Moon trying to prove something to himself, that he's an unstoppable machine of vengeance now. His end justifies the means speech isn't convincing, though.