Do you think modding this down is going to make those 100 million corpses go away? 'Cause it isn't.
Also, please avoid going on about downvotes in HN comments, as the site guidelines ask:
In truth, the point is a bit worn out and overused and doesn't say much about the underlying ideology.
The point is that it is irrelevant in the first place because the people he wants to lump in with mass murderers like Stalin or Mao or Khmer Rouge largely have never supported them or policies anything like theirs.
The discussion of numbers is pointless without first getting him to narrow down exactly what ideologies he is referring to by nature of actual policies implemented rather than by massive overloaded names.
The debating technique is equivalent to trying to argue that democracy is bad because the Democratic Peoples Republic of Korea is oppressive and tricking us into trying to turn it into a comparison of relative authoritarianism based on flawed, self-selected labels.
Instead it is the premise of what is included in the label you must challenge. It unravels quickly.