The rules as written seem to allow this, but I'm not so sure I'd allow it as DM. I'll have to think about it some more, maybe I'll change my mind, but my initial reaction is that Decree of Khirad is a charm, and charms haven't historically allowed you to injure the creature directly through its own actions. I'm thinking of the old Charm Person/Monster and Command spells specifically. You could force a creature to attack one of its buddies, but you couldn't make it commit suicide, for example. I know this line of thinking is based on completely different editions, but I think forcing a creature to attack itself violates the spirit of the charm. But certainly I'll concede that the RaW allow it.