I know we joke about war crimes here but remember that the way you conduct war and your image decides how many enemy reinforcements show up. Bad methods become recruitment ads for your enemies.
Also, I like how he said he would cut off their heads like he's going to get off his fat ass and do it himself. He's in a room with all his most powerful and capable subordinates telling them to kill eachother because he's obviously threatened by them. If they ignore him, grab him and lock him in his room for a time out while telling everyone he's ill, or just justify that fear of his then all he could do is spread his cheeks and beg them to be gentle.