Well said, but I fear an empirical study would fall into the same tribal polarities as "factchecking." What exactly should be laid at capitalism's doorstep? How about the two world wars? Which are the minor causes, and which are the major ones of any event? These become partly philosophical and thus not strictly quantitative issues.

But indeed, some basic facts could be determined to give us a more balanced view. I think this was the point of The People's History of the US, and The People's History of the World (two books written from the material losers' perspectives).