He liberally decided to reduce the number of casualties to the number of Jews who died in WW2 only and then went on to summarize all the estimated deaths during all communist regimes - even though they didn't all follow Marx' idea through and often relied on derived ideas consequently being altered, re-designed or created to fit the particular nations' cultural background - and put them against eachother. He forgets that exact numbers alone can be estimates and especially when it comes to human victims don't really qualify as severity scales. The reasons and circumstances have to be regarded as well which is why 67-80 million estimated deaths during WW2 will ultimately always weigh heavier than whatever higher numbers were produced during the times of various communist regimes. If the Nazi ideology had spread further, if they had won against all odds, then the number would have swelled to probably ten times then that. The relatively timely end of the Nazi reign was the reason why the numbers of victims of their ideologies couldn't rise further. Although you could argue that if lumping all communist and neo-communist regimes together is fair then lumping all fascist regimes would be too. Which of course does not work but those solely looking at numbers could get satisfied by it.