You can also think of it like a terrorist wanting to bomb people, would you have more success in a dense area or if everyone is spread out?
With more small sites, instead of a few large sites it spreads out communities and insulates them. With centralized networks, it create a "mother vein" where it's easier to plug into a large stream of users with little effort. No doubt capitalist extremists want centralized services too because they can convert everyone to their ideology, consumerism.
When extremists plan attacks they go to the central spots, when extremists recruit and build up followers they go to the places that aren't under surveillance. The latter is relevant for social media.
A decentralised internet would be a dream for extremist recruitment. It's equivalent to having an ungovernable community of millions sitting in your country.
Successful extremists do it in the light of day, out in the open. When you broadcast an idea that one in a hundred people will latch on to, and you broadcast it to five people at a time, you're not going to get much traction. When you broadcast it to five million people, you're going to get fifty thousand converts.
Notice how we are not having to seriously deal with a domestic ISIS insurgency (Because it has been very effectively driven into the fringe, where it has very limited reach), but we are currently having to seriously deal with... A lot of other ugly stuff, that has been very successfully spreading through mainstream networks.
It is 2016 election all over again, media chooses their favorite "evil" and promote it to death.
Decentralization stops radicalisation, because it allows free discussion.
That said, I'd invite you to continue your line of reasoning: decentralization leads to free discussion. Free discussion leads to X. X leads to the reduction in radicalization. What is the X you see?
For example I converted several hard antivaxers by explaining importance of each vaccine one by one. They agreed that at least some of them are important. They went to less radical position.
Another example was Brexit referendum. Populists had stupid arguments like 350 million/week for NHS, or about stoping immigration (UK was not in Schengen). It would be very easy for media to discus it, and debung those arguments. But instead of discussion and deescalating situation, they called oposition racist.
And even if you could keep up, not everyone will even engage. Folks don't want their beliefs challenged point by point -- it feels bad. It takes energy and commitment to be willing to hear challenges to ones own beliefs and not everyone has that ability.
And there's clearly positions that effectively reduce radicalization between fully open and "full China". There are also studies that say deplatforming is effective.
[1]https://www.reuters.com/article/us-usa-congress-twitter/twit...
[2]https://www.nytimes.com/2021/01/17/technology/qanon-meme-que...
[3]https://www.nytimes.com/2020/10/11/world/europe/qanon-is-thr...
I don't follow this logic at all. This is effectively how QAnon spread, as a niche group on fringe websites, before it grew to millions of users. A federated network gives better moderation tools to communities who actually want to moderate, but it leaves the radicalised communities free to grow, even freer than on a centralised network.
Another example I heard of were so called "free birth" groups with tens of thousands of women shunning medical help for births, even bullying women who wanted to seek professional help. As a result, quite a few children and women died during labour[1]
Private/semi private anti-vax groups are of course another huge issue right now. They often have hundreds of thousands of members. On a designated fediverse instance there is no possibility to shut this down.
I see no evidence or reason at all how the decentralised internet stops radicalisation or misinformation. It honestly to me seems like it would make it worse.
[1]https://www.thedailybeast.com/she-wanted-a-freebirth-at-home...