I warned you that someday there would be a pop quiz to see if you've been paying attention to me, and today's the day. Please explain what's wrong with this infographic:
The key result here is that 38% of protests turn violent if police are present, while only 7% turn violent if police stay away. It's the police who cause the violence!
It wouldn't surprise me if this is often true. But this statistic is meaningless. Police are obviously more likely to show up at protests that pose a high chance of danger in the first place. If you want the formal academic explanation, here it is:
Tests of dominant explanations of police presence using logistic regression analysis indicate that the best predictor of police presence at a protest event was how threatening the event was—police attended larger protest events and those that used confrontational tactics.
Confrontational events are the most likely to have a police presence, and confrontational events are also the most likely to become, uh, confrontational. That's all that's going on here.