Nurse fatigue can lead to accidents and errors.
Look up some of these position statements and research studies:
nurse fatigue - Google Search
I would say to the person attempting to mandate such unsafe hours of work, "I cannot work without sufficient sleep and rest. To do so would jeopardize the health and safety of my patients. If forced to do so I will, to the best of my ability, attempt to provide excellent care to my assigned patients."
If forced to do so I would put it in writing with the date, time, and the managers and supervisors who were informed of this. Make copies and give one to each person. Keep the original.
Maybe that will help them rethink scheduling unsafe hours.
I'm very sorry your employer puts the health of patients and staff at risk.