Cholera

In the early 1830s, Central American governance was dominated by progressives of European descent until cholera struck the Indians, who outnumbered the whites by a margin of ten to one. The liberals quarantined the worst-hit areas and then sent in medical doctors to save the inhabitants. Medicine, at the time, wasn’t helpful, and the Indians continued to die, which made them suspicious. They began to believe that cholera was a poison dropped into their wells by the ruling class. They formed into a mob.

Some natives believed that medicines were poisons used to finish them off. To be fair and to test this hypothesis, the mob captured a few doctors and forced them to consume all the medicines they carried. The doctors died, convincing the Indians that the plot was genuine. They revolted and won a bloody civil war and so on. 

That’s an unhappy history, but today, of course, we've evolved into a rational and well-educated society, one that elects capable leaders who can cope with the few remaining problems that arise.