The era before him prior to the japanese invasion invovled very large socioeconomical gaps--hence why communisim influence even grew.
While there are tons of terrible things that Mao has done, I don't think he is the worst thing to have happened to China. There are definitely people who have lost lives & led terrible lives, but there are others who stand to benefit. The cultural revolution was mostly uncalled for, but the Chinese civil war/revolution itself was not necessarily bad thing. The Cultural REvolution is only a part of what Mao had done. Without Mao, would China still be the same as it is today? Would it be better or worse than it is today? Who knows. I have relatives that had both suffered & gained. Some of the ones who suffered dislike the CCP and some of them are fine with the CCP.
While it is true that the communists probably would not have won w/o the Japanese invasion, Mao should be thanking Chiang instead of the Japanese. Without Chiang's inaction against the invasion, the people would never shift favor to the CCP. Mao may not have done better than Chiang in the situation, but he wasn't technically the "Ruler"of China as Chiang was. There were a lot of underground action with guerrilla warfare against the Japanese and the CCP did a better job at supporting them & garnering their support.
my uncle's wife's sister also married a Japanese guy, had two kids, and currently live in Nanjing. I wonder how the kids feel about the teaching of WWII in china, though.