What makes you think that user-moderated content won't be as toxic as algo-driven one? Look at reddit for example - the vast majority of content out there is posted to cause outrage, and people parrot it across the rest of the site.
On an actually decentralized platform the radicals would still be there, but so would many other voices. Where users can't be banned for "wrongthink", communities must convince their audience with arguments or fear losing supporters. The chilling effect would be gone. A truly decentralized site would have plenty of communities the individual user doesn't agree with - just like in real life. And just like in real life users can deal with it by staying away.
This makes no sense and is completely wrong.
Can you give some examples?