It is actually in many ways a terrific article, and there’s much to agree with, but alas, it includes an old chestnut that badly needs roasting and eating. (Or if it’s a horse chestnut, playing conkers with.)
Here’s the crucial, chestnutty sound-bite: “positivism depends on the reductionist belief that the entire universe, including all human conduct, can be explained with reference to precisely measurable, deterministic physical processes... Every schoolkid knows about what happened next: the catastrophic twentieth century.”
In case we missed the point, the article helpfully spells it out in the form of a pithy aphorism. “The dream of reason," it tells us, "bred real monsters.”
One hears this story quite a bit, but it wasn't entirely convincing the first time, and it's still not entirely convincing. Sadly, human beings did not wait for the arrival of Auguste Comte and Emile Littré before doing awful things to each other. During the Peloponnesian War, the Athenians systematically killed all male inhabitants of Melos and enslaved the women and children, a virtual genocide. In the Bible, the Children of Israel were busy wiping out every last Amalekite, with ostensible divine sanction. (Even today, incidentally, it’s a “mitzvah,” should you happen to encounter an Amalekite, to do him in.) And closer to home, the European settlers of this country were themselves guilty of a genocide, one which was clearly driven not by excessive rationality (or even by shadowy forces repressed by excessive rationality) but by greed, cowardice, and a not particularly rational belief in “Manifest Destiny.”
Let me be clear here: the positivists were indeed wrong about what reason could do. And the horrors of the twentieth century are indeed just that: horrors. My point is simply that you can’t blame the latter on the former. Nor, going a little further back, can you attribute the evils of the twentieth century to Enlightenment rationality, as some would like to. (It's worth considering that Enlightenment thinkers believed in tempering rationality with a heavy dose of “sensibilité”: think Adam Smith, think Rousseau.)
To be sure, twentieth-century science gave human beings the wherewithal to do a great deal of damage to each other in a horrifyingly short space of time. But it did not give human beings the motivation to do so. Human beings are simply built with the capacity for immense greed, selfishness, animosity, and the dehumanization of out-groups. Sometimes technology serves these terrible ends, sometimes it doesn’t. (We know what happened in Rwanda, where most combatants were armed with nothing more than machetes.) Sometimes “science” is invoked as justification, but sometimes it isn't. (As we've seen, religion does the trick nicely, and so by the way does “natural law”: again, think Rousseau.)
So why has this story been so popular? A number of reasons. Some people feel, quite reasonably, that Westerners today are devoting too much of their psychic life to phenomena that can be rationally parsed, to the detriment of a focus on emotions (sensibilité very much included); this infinitely reasonable view may generate more speculative views about just how bad the damage is. A second group, meanwhile, is clearly fighting a rearguard action, attempting to convince us that if we get rid of God (or "Being"), mass murder inevitably follows.
Above all, however, I think people love the old chestnut because it promises simple explanations for extraordinarily complicated phenomena. It satisfies a deep-going fantasy we have of being able to understand what happened in the twentieth century. If only we consider vast numbers of separate individuals as a single entity, it whispers to us, if only we see huge societies as a single organism, a virtual person (unconscious included), subject to predictable laws of cause and effect, then we will finally have the key to unlock the otherwise impregnable door.
Ironically, then, this story turns out to be generated by the fantasy that our reason can understand it all; at the end of the day, it’s just as "positive" as anything dreamed up by the Positivists.