Do you really think that Mao was completely cynical and didn't believe that what he was doing was "the right thing" that would improve the lives of his countrymen? Most people think they are doing "what's right," and some are willing to overlook unethical acts (or actions that let them accrue power to themselves) if it serves the greater good.
I tend to believe both these folks, and Mao for that matter, intend to do what they think is right & what will make the world better–and if you have to break a few eggs to make an omelette, so be it.
It's a comforting thought that there are "bad people with bad intentions who do bad things on purpose" and "good people with good intentions who do good things (and occasionally do bad things by accident)" but in reality these two groups are not that distinct.
(It goes without saying that these folks are not "as bad as Mao" I mention it only because it was already brought up as an example.)