A maxim for the twenty-first century might well be to start not by fighting evil in the name of good, but by attacking the certainties of people who claim always to know where good and evil are to be found. We should struggle not against the devil himself but what allows the devil to live — Manichaean thinking itself.

Tzvetan Todorov (1939-2017) Bulgarian-French historian, philosopher, literary critic, sociologist

Hope and Memory: Reflections on the Twentieth Century, ch. 5 “The Past in the Present” (2003)
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Paraphrased variant:

We should not be simply fighting evil in the name of good, but struggling against the certainties of people who claim always to know where good and evil are to be found.