> In short, average people behave the way they think they ought to, even though that behavior might not reflect their own personal feelings. Given a sufficient "A-HA!" moment when they discover that their personal feelings are shared by a large portion of the population their behavior may change dramatically. An example of this is the British colonists before and after publication of Thomas Paine's Common Sense. A year before the Declaration of Independence, America was full of patriotic British convinced that things could be worked out with King George, but on July 4, 1776 the colonies were full of Americans determined that they needed independence. Another is the relatively recent "Arab Spring."
As a white male who agrees with the general themes of the manifesto (even though it lacks nuance an depth) I refuse to work in the "valley" precisely because I will be an ideological minority; and therefore likely to be ostracized for my views.
When people are not comfortable with an oppressive regime they keep their moderate opinions to themselves. Voicing any opinion contrary to the Party line is dangerous no matter how extreme or moderate it is. So all dissenting opinions you are going to hear in public will be coming from extremists (e.g. "Have a Nuremberg-type tribunal for the Party's chiefs, lustrate the rest and their progeny for 7 generations!") because only the people who hold these opinions will be fed up enough to disregard consequences of their dissent. And there won't be many of them, since it's the definition of extremism to be in small minority.
However, for every single dissident there were tens or hundreds of thousands of silent supporters who would openly express their disgust and outrage over such horrific person but, when talking with their buddies in private, repeat and spread these ideas thus radicalizing themselves. Eventually everybody but a minority of "true believers" shifted from "well, life kinda sucks right now but at least there is no war" to "burn it down and salt the earth!". When this happened the whole mighty Communist empire collapsed within a year.
tl;dr When you see steam breaking through the seals you are about to experience the whole boiler's explosion. The steam that gets out first is weak but it's the sign of mounting pressure inside.