Select a leader. Doesn't matter how. Develop a system of correct behaviour. Netiquette. Write it down. Display it publicly.
Congratulations, you are now a group of betters. You can tell because you behave better. Note this requires having actual confidence: when someone says, "You think you're better than us? Huh?" You just go, "Yes." Asserting uncommon nobility via your own authority, not attempting to borrow anyone else's.
Anyone who hasn't done this and isn't attempting to do it simply isn't right-wing. They may be less-left than open Fascists, but they're still left-wing and thus defective anti-civilization agents of dissonance.
1. Have rules, as defined by an explicit ruler.
2. Follow the rules.
You don't even need to host your own forum. You could invade someone else's. E.g. leech off the Steam forum of some old, defunct game.
Is this a tall order? An extraordinary demand?
By performance, yes, apparently it is a very tall order.
Note that I suggest a public forum paired with a private forum. The public forum should not contain politics. No culture war stuff of any kind. This means nobody can justify a ban. This also allows folk to apply to the public forum as a way of earning admittance to the private forum. If they can sufficiently obey the etiquette on twitter or whatever, they get a first-level invite. If they can maintain it, a second-level invite.
The netiquette should define proper, effective, and pleasant communication on the internet. It should persecute tropes and methods that lead to degenerate behaviour. Engaging in a flame war is bad, and baiting a flame war is simply also bad. Waste of typeface. "Seemingly" innocuous is not good enough.
There should be a list of polite forms, and their purposes. Why was politeness defined this way, and what is the purpose of the definition; what does it aim to accomplish? It is sufficiently simple to define effective communication if the ruler has determined what communication is for.
The politeness should not be so rigid that it prevents the development of friendships, or other forms of intimacy.
There should be specific penalties for various breaches. When do you politely pretend they didn't? When do you laugh at them? Short ban? Hard block? Why?
I personally suggest grading on a curve. Higher standards for higher ranks. Outsiders get a lot of leeway, unless they want to become more inside.
The code of behaviour doesn't need to be perfect. Doesn't need to be the One True School of Talking Via Keyboard, it just needs to be profitably better than roll-your-own.
The purpose of the public forum is primarily to model effective behaviour. The internet sucks because everyone behaves like a spoiled brat. Everyone is a troll, it's merely a matter of degree. Adhering to an actual code of conduct is actual virtue signalling. It won't work as a model, exactly, but it will sure let you be a snob, because anyone who tries it will find it really does work better.
Nevertheless, it should at least allow the possibility of working as a model. This is the second reason for the politics ban: the code itself should not be tribally marked. It should work for anyone who cares to try it. That is, unless they're inherently dissonant. You can't have a code without tribally marking as being pro-standards, which some tribes are inherently opposed to. The code should be tribally unmarked as far as possible, without straining to go farther than is possible.
The third reason is that politics is a canon impolite topic, for good reason.
Politics is religion. Being irrational is the point of every religion. (Except Alchemy.) You can't 'discuss' politics, you can only preach, and unless your audience formally agrees to be your flock, it's only going to lead to an irrational flame war. That or they 100% agree with you, making the discussion epistemically a non-discussion; zero information conveyed.
The private forum can offer preaching dispensations, however, allowing the "discussion" of politics.