Paul Craig Roberts has an item about Mao's atrocities against his own citizens here.
But Mao was a Communist, and thus beloved of the left. And if you want the left to get all huffy, all you have to do is question a) their motives, or b) their patriotism. Why so touchy?
I just want them to question why people would question these things, and if there's any possibility that such questions are based on something besides reactionary politics.