The problem with the title is that it refers to something that isnt backed up by most of the reliable sources cited  The only real source for the theory expressed in this title is Valentino thus as I suggested before a better title would be something like Valentinos theory of mass killing or some such  Other sources are connected if we make the title Mass killings in the Soviet Union China and Cambodia that way we dont have to have the sources all agree that it is communism or totalitarianism or democide or whatever that is at the root of all this  Its true enough that these three examples are cited by different authors together  But some of the editors here seem wedded to making this article express a political theory about communism that just isnt backed up by the sources