Effect of External Shocks on Norms on Online Hate Speech

We examine the evolution of hate speech in an online forum before and after the Islamist terrorist attacks in Germany in Ansbach and Würzburg in July 2016. In the first part of the study we use pre and post attack data to identify a breakdown of social norms on hate speech expression. Hateful comments towards immigrants and Muslims increased after the attack. Surprisingly hate speech towards unrelated minority groups, such as LGBT and womens' rights also increased. We interpret the findings as a breakdown of norms against the public expression of prejudice towards immigrants, which causes a spillover to other domains. In the second part of the study we compare the effectiveness of censoring prior hate content as an intervention to reduce hostile content before and after the attacks. We argue that censoring hate content biases the individual's perception of the prevalence of hate speech, therefore highlight a descriptive norm against it. Results show that a high level of public debate on a topic, such as media coverage, is linked to both an increase on hate expression and an increase of the effect of environmental cues on related normative behaviour.