I am not going to site Stalinist Russia or China as examples, because they are not true communisms, merely dictatorships in disguise, but I am going to site human nature.
: But can you prove there is a human nature?
Can you prove that the Earth is not a figment of my imagination? No, but through observation you make assumptions along the lines of other people exist. Equally, one can make observations about human nature.
: And if you succeed at that, can you prove that it is YOU who knows what human nature (for anyone other than yourself) actually is?
Do I know more about human nature than anyone lese? Depends on the person, I know that I am not alone in this belief, and that what i wrote is my observation of the ay other people behave.