Table 1. Characteristics of all training datasets.

DOC was first trained on 16,000 tweets collected during the Brett Kavanaugh confirmation hearings. We then tested generalizability and retrained on the combination of Kavanaugh and all other topics (26,000 total tweets).

Topic	Description	Tweet date range	Political ideology of users	Tweets containing outrage	N
Kavanaugh	During the confirmation process for the Supreme Court, nominee Brett Kavanaugh was accused of sexually assaulting Dr. Christine Blasey Ford. Both parties testified to the Senate Judiciary Committee, and Kavanaugh was ultimately confirmed.	15 September to 18 October 2018	Mixed	52.00%	16,000
Covington	White high school students wearing “Make America Great Again” hats were filmed appearing to harass a Native American man in Washington, D.C. After the video went viral, subsequent footage suggested that the interaction was more complicated. Several media outlets issued retractions.	22 January to 1 February 2019	Mixed	26.36%	2,500
United	A United Airlines passenger was forcibly removed from an overbooked plane. Footage of the event showed the passenger being injured. The video went viral and elicited backlash against the airline.	10–14 April 2017	Mixed	20.08%	2,500
Smollett	In January 2019, actor Jussie Smollett claimed to have been the victim of a violent hate crime perpetrated by supporters of President Trump. Investigating officers later alleged in February that Smollett had staged the attack.	22–26 February 2019	Conservative	23.00%	2,500
Transgender ban	The Trump administration’s ban on transgender individuals serving in the military was upheld by the U.S. Supreme Court, reversing the 2016 decision by President Obama to open the military to transgender service members.	22–25 January 2019	Liberal	52.60%	2,500