"I think it's easier to discredit a private delusion in public (where an individual may receive feedback from multiple individuals)."

It appears that it is not easy but impossible instead. The believers of the "private solution" stand firm to their argument. They do not come back as the result of a discussion. Instead they take every discussion as a "win" confirming and legitimizing their views. And they attract new believers that way.

So it would be better to restrain these groups into meeting space not so easily accessed by everyone to stop those crowds from growing.

It's not only the Flat-Earthers got rescued by Web 2.0. We have several stories here in Germany about prominent people who turned into Corona-deniers within several month and became leading persons of that movement due to their popularity. But they did not start the fire. They got attracted by it burning already like many others in that movement.

And it is psychologically understandable IMHO. There is someone annoyed by the corona-restrictions in place and questions their legitimacy. Reliable information about Corona comes from official sources but those are run by the same people who ordered the lockdown and the restrictions so he is sceptical. Along with that information he finds a hell of a lot desinformation about Corona as distributed by Corona-deniers and as this supports his anger about the restrictions, he sticks with that. That is how that poison works.

It is the same with climate change or Trump losing the election. People are annoyed and turn to the internet for redemption. And than it happens.

The desinformation on the internet moves people into more extreme positions on many topics, most often by denying facts and making up an alternate reality. It turns annoyed people into extremists. That is a big problem.

Did I defend my argument?