Not a direct response, but a response as part of a larger philosophical narrative.

He was a true believer in a society driven by rational discussion and the free exchange of ideas, which was the main point of his work.
As part of describing how he thought society should be run (tldr: we should discuss things, change institutions peacefully, and make small changes that we can actually tell if they worked instead of upending society in the name of an untested ideology) he spent some time describing the edge cases and weaknesses, which is where the quote comes from.

He wrote the work during WW2 after fleeing Germany, so there's more than a little implied context that people would have at the time of publication. Basically a general vibe of "what the fuck! Let's not do that again!"