As should be clearly indicated by the message quoted in the post you replied to, the goal in question is to prevent mass shooter levels of radicalization. As mass shootings only take one nutjub, the better path is largely to leash the nutjobs in how far off the deep end they can go, rather than concentrate them so they can keep getting more and more extreme without warning. The more public the discourse, the better, because it can be monitored when it's public.If your goal is to stop new members wandering into an echo chamber, then making said echo chamber harder to find is going result in fewer people wandering in.
Do you actually believe that deplatforming and censorship don’t work?
And if there is no echo chamber, because there's no need for it from not having the mainstream primary public discourse platforms banhammer dissent from Silicone Valley morality into the underground, then people aren't wandering into an echo chamber. They're running into crazy new ideas, and the counterarguments to those ideas. You're never getting rid of echo chambers to an effective degree without total censorship authority like China has, which no Western country possesses, and when the question is "how do we stop the radicalization into mass shooters", it's extremity that is what is being targeted with this questioning, not scale. It doesn't matter how many alt-right people there are in this case, what matters is how far off the deep end they go.
When we are talking about the extremes of radicalization, the solution is to prevent echo chambers where the extremes are driven further. To have disruption in radicalization from the opposed viewpoint being present. When we're talking the pervasiveness, how often people able to be considered part of some group, then confining them to echo chambers works better, as there will be fewer in absolute numbers, but there will then be a higher rate of outliers like mass shooters because these echo chambers breed genuine extremism. And if they manage to gain power despite such confinement, it will be used for far worse abuses, regardless of how limited it is. And they won't be fixable, because they justifiably assume conspiracy against them, where permitting them to speak in the most public of places (and get shitcanned by the public, but they're able to speak and being shat on by their peers instead of giant corporations they have no ability to impact) would undermine that assumption.
Ultimately, the reason Stormfront exists is because we already ban neonazis off all the major public platforms. If they weren't, they wouldn't have these highly-concentrated echochambers that people who only touch on some of the positions get forced into and made to adopt all the nonsense because they can't talk to people outside the echo-chamber. If you just oppose trans normalization, the advocacy of treating them as no different from cisgender persons despite their demands for medicinal treatment and wish for them to be recognized as a medical abnormality like every other case of needing medical intervention for a comfortable life, and get banned off Twitter and Facebook for this difference in why and details of how to accommodate them, then get stuck with /pol/ as your only place of discussing politics, you'll end up drifting to far more extreme positions, and far more of them. Because you no longer get exposed to the humanizing of transgender persons, and begin being exposed to the ideas of purging the lesser-able instead of accommodating for what they're below par in, alongside all the other extremism without opposition.
And yes, that's me describing my view own on transgenderism. Accommodate them as a medical abnormality. Like every other situation where people need chemicals pumped into them to feel comfortable with life. We do it for highly specific mental deficiencies in stress management and mood stability, what logical reason is there to not include people who feel an incongruity with social expectations of the sexes and which one they physically are that is severe to the point of impairing social function? Lets them benefit from all the existing systems for handling medical abnormalities, and the arguments that this is somehow dehumanizing are themselves arguments that dehumanize all the other abnormalities. Like my own autism. So if you think my position on transgenderism is "transphobic", you're implicitly ableist in a way that is specifically applicable to me, personally, by thinking that being categorizing as a medical abnormality for neurological abnormalities causing significant divergences from social norms is a bad thing in its own right. Or that abnormality is equivalent to inferior, which also disparages me and those like me for our fundamental difficulties with comprehending social interaction as it occurs among the neurotypical.