Mao was responsible for the deaths of 30-50M in famine. Estimates of Stalins score from famine, execution, forced relocation, labor camps is more difficult to ascertain. Estimates range from 3 -20M. Whether you disagree with this estimate it is incredibly likely that the prior poster was referencing the 33M–70M who died in intolerable conditions not the nazis.
The fact that you justify the state getting in the systemic murder business for any cause is a fundamental difference between our understanding of what can ever be morally acceptable.