This has nothing to do with the poverty rate or material prosperity–it has to do with intentional killing. These are pretty good numbers on the human killing in the twentieth century (and it doesn't count the wars) – a mountain of corpses that could be seen from Mars: http://bit.ly/1taG4I7 I don't think the “humanity just went crazy for a spell” is the kind of thing that comforts anyone – in fact that little aberration is what caused people to reject your optimistic Whig or Progressive theory of history --- that man is moving ever upwards toward the light (or on a smaller level the classical liberal idea of peace through shared economic interest) or Fukuyama's "end of history" after the fall of the Berlin Wall -- an end -- the unraveling of which has been the story of the twenty-first century to date -- accelerating in the last eighteen months!
I don't think anyone should be sanguine about the end of mass murder when enough nuclear weapons to blow the world three times over are stockpiled. And after the massive disappointment of the twentieth century (at the beginning of that century the sunny consensus was there would never be another war –people were just too rational and had too good of a system set up) the idea that an economic system is going to save the world is not very comforting nor intellectually satisfying – it sounds like just another version of the utopian promise of Marx, et al. --which in fact it is, having roots in the same intellectual stew:
“The collapse of the Soviet Union in 1989 -- symbolized by the Fall of the Berlin Wall -- was an event of major historical significance....The end of the Cold War unleashed an understandable euphoria. Francis Fukuyama called it 'The End of History' (namely the triumph of liberal democracy marking the end of what to him was the dialectical progress of history). President Bush Sr. gave expression to that general euphoria, when he spoke about a 'new world order.' Cardinal Ratzinger's response was a raised eyebrow and a question mark: Oh, really? How can we talk about a new world order, if, as he argues, the West, despite differences in political and economic structures, in fact shares the same intellectual assumptions as the Marxist East?” ~ D. Vincent Twomey, in “Pope Benedict XVI/Joseph Ratzinger on Politics” (Gerety Lecture, October 23, 2013) http://bit.ly/2e5Xw1a
Ralph Wood and Flannery O'Connor are also referring to abortion – a massive extermination of human life that goes on largely in antiseptic silence, but has widespread cultural,political and moral fallout.
Read Professor Wood's essay, which I linked, if interested in his entire argument.