The point I'm trying to make is not that there are particular topics where the respectable opinion is so mendacious and delusional that they're impossible to discuss rationally in public, or even in any respectable company. (Although that is clearly true.) I am actually making a stronger claim.
Namely, some such topics exist in every human society, but their scope does vary a lot -- and if their scope is sufficiently wide, an upfront and rational public discussion of some very general and fundamental questions about government, society, and human affairs becomes impossible, since such a discussion would necessarily involve countering some of these established delusions and mendacity. My claim is that at some point during the last few generations, the English-speaking societies have in fact gone past that point. (This also applies to other Western societies, since there are no other ones whose intellectual institutions and traditions have maintained independent continuity through the 1914-1945 cataclysm.)
Again to use the Soviet analogy, imagine having a discussion about general and fundamental trends in modern history in which it would be an unimaginable heresy to open the question of whether the Russian Revolution in 1917 was perhaps not such a great and fortunate event after all, or that maybe Soviet socialism in fact wasn't such a great and liberating improvement on the Czarist government, or that (gasp!) workers are actually better off under capitalism. Clearly, it would be impossible to have a sensible discussion that maintains a solid grip on reality under such constraints, and the result would be a mere rehearsal in ideological cant. What I find is that the effective constraints on respectable public discourse nowadays are, for all practical purposes, equally suffocating -- although of course they are enforced by much less crude, explicit, and violent means, which rarely go beyond shunning and marginalization of dissenters.
(Also, here I don't have in mind just topics that are so incendiary that dissenting opinions are likely to raise firestorms of outrage and condemnation, but also other ones where the uniformity of respectable opinion is so well-entrenched and secure that someone opposing it will be affectionately and self-assuredly laughed off as an annoying but harmless crackpot, with comparably small repercussions.)
SIAI benefactor and VC Peter Thiel has an excellent article at National Review about the stagnating progress of science and technology, which he attributes to poorly-grounded political opposition, widespread scientific illiteracy, and overspecialized, insular scientific fields. He warns that this stagnation will undermine the growth that past policies have relied on.
Noteworthy excerpts (bold added by me):
In relation to concerns expressed here about evaluating scientific field soundness:
Grave indictors:
HT: MarginalRevolution