So, if the emotional empathy should be discarded, why should I help all those strangers? The only answer that the link suggests is "social propriety".
But social propriety is a fickle thing. Sometimes it asks you to forgive the debts of the destitute, and sometimes it asks you to burn the witches. Without empathy, why shouldn't you cheer at the flames licking the evil witch's body? Without empathy, if there are some kulaks or Juden standing in the way of the perfect society, why shouldn't you kill them in the most efficient manner at your disposal?
I completely agree: asking people to discard moral emotions is rather like asking rational agents to discard top goals!
Wikipedia says that "body-counts of modern witch-hunts by far exceed those of early-modern witch-hunting", referencing: Behringer, Wolfgang 2004: Witches and Witch-hunts. A global History. Cambridge: Polity Press.
My point being that our emotional empathy is already out of tune with social propriety, if you consider the social norms typical around the world and not just among rich, Western populations. Let alone the norms common in the West for most of its existence, and so perhaps again in the future.