Evidence that expressions of moral outrage are in part self-serving.

Ethics and morality are commonly associated with altruism and pro-social behavior. From this perspective moral judgments are regarded as fundamentally selfless or at least group-oriented. When people express moral outrage at the transgressions of others, their expressions may arise from deep-seated intuitions or strongly-held values, but in either case it is assumed that the purpose or function of such expressions is to punish the transgressors and promote social cooperation. However, in this study, Paul Bloom and colleagues provide experimental evidence in support of a theoretical model according to which expressions of moral outrage are fundamentally selfish in nature. People who invest time and effort in condemning those who behave badly are trusted more. Thus, condemning transgressors for their bad behavior is a way of signalling to others that one is trustworthy, which can bring advantages to one in the long-run.

Original Source:
Jillian J. Jordan et al., Third-party punishment as a costly signal of trustworthiness, Nature, November 2015.
http://www.nature.com/nature/journal/v530/n7591/full/nature16981.html

Summary description by authors:
http://www.nytimes.com/2016/02/28/opinion/sunday/whats-the-point-of-moral-outrage.html?smid=fb-share&_r=3