You're almost given yourself too much credit as RF is remarkably conformist and has a stable consensus of views but doesn't have conscious and deliberate regulations of people's views. So RF spontaneously tends to reflect the mainstream views in society, though it is slightly left-of-centre for the USA. There is an almost Darwinian process of natural selection of opinions favouring the consensus with non-mainstream views getting selected out by the social pressures involved. But just start a thread saying homosexuality is unnatural and immoral and watch the torrent of posts extend in to dozen of pages of outrage. There are clearly areas of debate where you "aren't supposed to go" on here even without rules prohibiting it. Or just say how wonderful Trump is, or praise Hitler as a "caring leader" who supported animal rights and was a vegetarian. Stand back and watch the fire works!
Meanwhile, on communist and fascist forums there is often some degree of exclusion of "non-believers", such as in an "opposing views" sub-forum where they can congregate but aren't able to access the rest of the forums. (It's like a "free speech zone" or "gulag" where people can't do any damage). These kind of regulations are partly down to security considerations as you don't want any personal or identifying information getting leaked as that can have real world consequences such as losing your job, getting black listed and is thankfully rare occasions, violence. It is also because having people who
roughly agree makes for a more stable and durable community.
Assumptions about tolerance and pluralism generally only apply in relatively liberal and mainstream contexts, whilst other communities function reasonably well without it. Even with such stringent limitations there can be a vast disagreements between people and these groups are far from homogeneous or monolithic. e.g. Stalin versus Trotsky debates are as common on communist forums as efforts to "define" atheism are on RF. Christian forums appears to have a small minority of flat-earthers based on debates on scripture. And so on.
To one degree or another,
all forums involve some level of "dictatorship" over what you can or cannot say. RF officially forbids swear words and the word filter catches most of them but doesn't go after specific political or religious opinions. Other forums do so with varying degrees of wisdom and effectiveness.
