Most of the 100 million that died under communism was due to poor planning resulting in famines. Yes, communists killed a lot of people but the Nazis explicitly planned and carried out an industrialised system of murder.Communism killed 100 million people in the 20th Century - why do you think Lenin and Trotsky (Mao too) are not as vilified as Hitler? with his "paltry" 55 million killed?
Mao I think gets less talk due to Eurocentrism. The west tends to think of the east as mysterious and barbaric and takes little time to look into their affairs.