As much as I dislike that character, who did it in because of powerhunger of himself, a) MC would have done the same in his shoes and b) he just did prevent another bloodshed. Okay, it would have been a smaller one given that that arsefart lord (I won't call him Batman, as he is no Batman.) will build up his defenses, but peace is peace and who knows what happens next. (My guess is, that new guy will attack.)