No one ever tried to say, "Hey, let's take a step back and look at what the culture as a whole does".

1. That would have involved conjunctive predictions about such a society I'm not confidently able to make, or worse, assuming that everything else stayed constant when discussing counterfactual scenarios.

2. As I said there, I think you overestimated the extent to which people's goals overlapped, and terms like "general egalitarianism" hid that (first, because 'general' allows for everyone to imagine the term describes things occurring with their preferred amount of exceptions to accommodate differences, and second because 'egalitarianism' allows everyone to imagine that their preferred level of influence is applied to make outcomes equal and their preferred amount of unconstraint allows greatly unequal outcomes).

3. "the focus consistently remained on the specifics." I saw a main purpose of your arguing that there are great areas of agreement at the beginning a meta comment like yours to be to establish a necessary, or at least very helpful, groundwork for the possibility of constructively engaging at the meta level. Assuming you agree, you might agree with my drilling down to specific scenarios as being the most constructive thing granting my opinion that nothing close to such a consensus exists.

   A societal level discussion requires agreement about many related things in a dynamic system, and would be great provided people agreed on values. However, some people believe that, e.g. there is no difference between manipulation and persuasion (waves), or that consciously artificially ('faking') social signals constitutes rape when someone has a relationship with the signaler based on his signals (or even if they in fact weren't a necessary condition for the relationship? I'm not sure). I don't think it would be productive to go from there to speculation about types of society in which each individual has the opportunity to bend their (unfalsifiable) predictions about what would happen to conform to his or her political view.

   I understand you think it likely negative utility of PUA at a societal level might swamp even the local utility it produces and render that argument moot, but I really think people had thought of that and rejected it. We were really stuck on the lower level and I don't think it at all likely things would have been better at a higher one.

4. As I recall, others did bring up the macro view, though disproving "No one ever tried to say," might require sifting through over a thousand comments. Something like "three times as many," as you said, might be accurate to reflect the fewer meta-level comments but if true that would make the PUA example an anomaly even if it were true.

argue politely

I think this can become a lost purpose to some extent as the purposes of arguing politely are to ensure content rather than tone is the focus, people don't become angry and think unclearly, etc. Autistic spectrum people who primarily care about ideas don't need to care about tone as much, particularly when replying to others whose personalities they already know.

I am home for thanksgiving, just the other day my family was making sandwiches. We were pulling ingredients out of cabinet, setting the table etc. and my mother was taking things out of the refrigerator. She began putting onions, meat, etc. on the counter, but what drew the eye was a large clear freezer bag containing several pounds of sliced tomatoes, and while taking things out of the fridge she asked me, "What would you like to put on your roast beef sandwich?" "Tomatoes," I replied. "They're on the counter," she said. "I know," I said. She looked at me. I looked at her. Oops I thought to myself, I'm doing it again. ;-)

The point being that I'm happy with the way people sometimes rudely disagree with me here. I'll concede a great deal as far as how I'm used to speaking with others not being appropriate for those I know nothing about, or my perhaps too-blunt mode of speech even when it is appropriate instilling poor habits I embody when it isn't appropriate, but one can't strongly conclude things about the content of discourse from its form.

The problem of being an echo chamber is only tangentially related to politeness.

Because people post consensus views more often, people tend to agree with the consensus more.

Have you read Every Cause Wants to be a Cult, EvaporativeCooling of Group Beliefs, Groupthink, etc.?