Mao is dead. Your friend chose to believe in him; Mao did not force him. Most of Mao's killings came under the Cultural Revolution, and that was a few million (2-5?). Though it was most likely more than Pol Pot, it was a much smaller portion of the population, which must be taken into account. Moreover, the 20 million who died from the Great Leap Forward died from bad economic planning, not outright execution and planting landmines around the countryside. Imagine if Pol Pot ruled China instead and covered the whole country with landmines and evacuated the entire population of Beijing, as well as banning anything that remotely resembles modern technology. The two are incomparable in my mind.