The Spanish flu of 1918 killed 25-50 million people. World War II killed 60 million people; 107 is the order of the largest catastrophes in humanity’s written history. Substantially larger numbers, such as 500 million deaths, and especially qualitatively different scenarios such as the extinction of the entire human species, seem to trigger a different mode of thinking—enter into a ‘separate magisterium’. People who would never dream of hurting a child hear of an existential risk, and say, ‘Well, maybe the human species doesn’t really deserve to survive.’
Eliezer Yudkowsky, ‘Cognitive Biases Potentially Affecting Judgement of Global Risks’, in Nick Bostrom and Milan M. Ćirković (eds.), Global Catastrophic Risks, Oxford, 2008, p. 114