Nobody disputes that what Mao's rule became later in life was horrible, brutal, and despotic. But the tragedy is that what he became later in life was a betrayal of what he stood for in his youth. He started out as an idealist, genuinely trying to build a better world, and back then he had the sense to realize that the only way it could work was as a gradual transition taking generations. But as he aged, and perhaps as he grew accustomed to being in power, he lost sight of those old convictions, and he tried to forcibly accelerate the pace of change so that he could see the results within his lifetime, and the result was a horrendous nationwide atrocity. His younger self would've known that was the wrong path, but power corrupts.
What is your source his early idealism? I only read his Juno Chang bigraphy. Also there was something off early in most dictators, like Stalin.
Pretty much every historical work that forms an opinion comes under heavy criticism.
I wery much doubt that any idealist could commit crimes as horrific as Mao.