Is it really communist beside the name? I wouldn't say it is and the very important increase in the wealth and salary gap between classes shows that it's far from being a communist regime nowadays
As for Tiananmen, one needs to see the context. China had recently endured the cultural revolution and the leaders had a good understanding of the potential disasters of a revolution. In that context, if they believed that the ends justify the means and that millions would die if a new revolution happened, the leaders could rationalize their decisions.
I'm not saying it's not horrific. It is. But, it's the kind of decision that needs to be understood in it's historical context.
As for the actual mowing of bodies and the bulldozer's making a pie. I'm not sure if it's real or not. It does seem like the kind of rumors that circulate because they are particularly gruesome. What would be the point for the Chinese government to do that? I may be mistaken but, in my mind, the Chinese government at that time was nothing if not practical and pragmatic (in a horrifying way for sure), there would be no justifiable reasons for being this gruesome.