So whilst going to rescue the Moth Priest 'Dexion Evicus', I think I accidentally might have hit him, not sure how. Anyhow the bearded maniac has taken this as a personal attack and refuses to accept a yield. Because he's so angry with me he'll just not quit, but being a quest NPC he can't die, nor can my companion Mjoll. So aside from the hilarious infinity battle, I thought, fair enough I'll talk to him whilst he's 'downed' and lo, I progressed the quest.
So I go back to the Dawnguard fortress, and he's there in the middle shouting murder and attacking everyone in the fortress! Clearly his rage knows no bounds.
Is there a way to forcibly pacify him without interring him? Or do I need to roll back and do over?