Upvote:2
The very term "Reign of Terror" means he is almost certainly thinking of the French Revolution. The term refers to a period of the French Revolution in which the revolutionaries carried out massacres, arbitrary arrests and killings, show trials, and much else in the name of "freedom for the people".
The French Revolution fits the bill really well. Most people would admit that the French people were oppressed before the Revolution, and that something needed to be done to free them. The Revolution was perhaps created through 'pity' for the ordinary people. But the results of the Revolution included terror and tyranny, something actually named the "Reign of Terror".
Other revolutions, including the Russian, might well have been in his mind as well.