I tried to give a quest in when I realized I was a level 4 vampirw so I left setstage so that the vampire cure thing happened and went back in and he was still hostile I tried stopcombat I even tried changing HIS race to a vampire but he stayed hostile.
Try, instead of tricking the game like that, just going and feeding somewhere and then try it... Or try and legitimately doing the quest without console cheats to get cured of vampirism...