In a world of literal magic compulsion, it becomes a bit like if it were possible to say program someone to be a serial killer and they acted as an effective bio-robot doing as commanded to do so.
Even in a court of law today, that would be a major factor if one can be considered guilty. Granted that isn’t really a thing IRL, mind control that is in literal terms I don’t think is yet real.
If say some computer chip thing could be put into the brain that could allow another to remote control another person, influence their thoughts or even compel them to do things and put ideas and actions into them, then certainly we could REALLY hold the person whose physical body did anything as totally responsible.
Heck, Orcs in lore had far greater direct knowledge as to what they were signing up to and were not as directly under the magical influence of a literal equivalent of a God as the Eradar were, and have gone in for Demonblood drinking twice and the Horde collectively both has done genocides without direct magical mental control a few times now; and is still nominally hostile to people they’ve warred with purely because they were serving Space Satan, even without Demonblood and mental compulsion and we grant Orcs and the Horde a pass.