If you can't remove it you can think in the other way, not killing your enemy's you can give them another chance by selling them as slaves, in this way they can think at the wrong chooice they made by taking a battle with you and at least they are not dead...
Or, I think you can modify the chat with the slave trader and his name (not sure about it but you can search for this) and you can put his name like Rehabilitation Officer and the chat like "Hey dude I have some enemys with me and I wanna give them to you for rehab"....or something