It would be interesting to find out how such incidents are treated by courts and insurance companies. This way one could establish what constitutes negligence.
I am convinced that doing it just by yourself (even with chocks) would be considered to be negligent. Doing it with a passenger in the cockpit might be even worse. If you know what you're doing and you having a knowledgable person in the cockpit (not necessarily a licensed pilot), you should be OK.
Many people don't know that the prop can snap backwards, that is a major source of accidents when hand-propping. The concept of the top dead center isn't widely known either.
I have a C172M where charging the battery requires me to disassemble half of the airplane and I have hand-propped it many times. This usually attracts a whole crowd of spectators, 90% of whom consider you to be crazy.