I'm more worried about the lower tail end of the bell curve that doesn't get the memo, and they become increasingly deranged. When 1/4 of the public is essentially brainwashed, your society is in deep trouble.
Yeah, 25% is way too low a threshold for brainwashed to be useful to those at the top. They need at least 50%, 70% would be good but 90% is ideal. Society being defined as in peril is basically a rhetorical constant however.
On a more serious note haven't societies long been based upon common brainwashing? The Bronze Age and before are fuzzier on the details but propaganda certainly existed then as well at a smaller scale.
People don't seem to understand the massive amount of specialization that's occurred with humanity, especially since the start of the industrial revolution. The most distant you go in the past the more general your title was, for example farmer. Now you can have some extremely narrow field, say EUV lithography, and if you and the other 10 experts on it on the planet decide to go bonkers you could cost billions of dollars to the processor industry.
On a more serious note haven't societies long been based upon common brainwashing? The Bronze Age and before are fuzzier on the details but propaganda certainly existed then as well at a smaller scale.