Bloomberg had an excellent piece by science journalist Faye Flam, titled It's an Outrage! See? Look How Outraged I Am! Her lead is "Science is starting to shed some light on the curiously continuous cycle of moral outrages." Expressions of collective outrage are not particularly new but it does seem to me the frequency of expressed outrage, and outrage over more and more trivial events, has increased. Why? Psychologists offer this thought:
Psychologists say it all starts to make sense if you think of outrage as a form of display. Expressing it advertises a person’s views and allegiances to potential allies. And the more popular a victim's cause, the less risky it is to join in displaying your umbrage.
Why do some incidents provoke almost universal outrage and others set off only those in certain age groups or of particular political leanings? One of the most universal sources of outrage is stealing or hoarding resources, said psychologist Eric Pederson. The theory is that this is ingrained in humans because our ancestors' foraging cultures survived by sharing; if Joe helped himself to what others hunted and gathered, but then did not share his good fortune when he found berries or killed a wildebeest, he’d get in deep trouble.
Humanity’s deeply rooted antipathy for cheaters helps explain the outrage over the tax evaders revealed by the Panama Papers. But in other cases, said psychologist Robert Boyd, the definition of what's outrageous is dictated by less objectively obvious cultural norms. Humans are wired to pick up cultural rules and norms, and to aim outrage at violators, he said. Cultural norms vary by political leanings, geography and other factors. Often there’s a large generation gap.
Harvard’s Krasnow said it all comes back to the fact that displays are aimed at potential allies. An outraged person may have no personal tie to a given issue, but outrage can signal sympathy with those who do. This can be quite noble and selfless, not entirely self-serving; the two blur together in ways that allow human civilization to work to the extent that it does.According to an anthropologist I read, human reason evolved in the context of communal survival. People observed patterns in events around them and developed heuristic models for survival. They fashioned stories to make sense of events and their place in them. Reason developed as a way to reinforce stories and strengthen societal cohesion. Which is also to say, reason that challenged societal stories and cohesion was a threat. We are not naturally wired for objectivity.