Of course what passes as modernity today would have been considered progressive back in the past, but you fail to mention also that many such of those debates back then also never panned out and fizzled out (aka non-substantive), while others were actively fought against and rolled back.
The French Revolution, Communism, Fascism, The Cultural Revolution, society at many points has historically pushed back against radical progressive visions that ultimately turned into horrific failures that the majority opposed. And the helm of many of those movements were power-hungry Authoritarians, aka the "Aggresively-Conventionally Minded" PG is referring to. The point is that radical progressive movements often provide the unfettered space for Authoritarians to act out their own worst impulses on society, the Reign of Terror and the Cultural Revolution being a prime example.
That's why also the point of "conscious bias against defining new forms of heresy" is just reiteration of the etablishment view of slow, iterative change vs highly disruptive change, of which the former can more effectively keep authoritarians in check. This is not a paticularly controversial view either.
The point is that for PG, and for the majority that voted Trump, Wokeism isn't working, it's not the direction that people wish society to move forwards in. I don't think it's analogous here to Civil Rights or Feminism either because it's a question of speed rather then change. Equality via Long-term Integration (& Homogenization) vs Equality via Aggresive Multiculturalism, and I think people prefer the former.