Free speech used to be fine because people used to be exposed to alternative opinions. Now people get put into bubbles by algorithms which show them more of what they want, rather than giving them a healthy diet of diverse opinions. Without that, some people can be easily led to believe any old propaganda and radicalised. The check on extremism has fallen off thanks to personalisation creating echo chambers.

For that reason, a P2P Twitter-type platform where accounts couldn't be removed would be potentially very dangerous.

I would rather try to deal with free speech by looking at personalisation and filter bubbles, perhaps mandating some kind of diversity gets baked into algorithms, which seems to lie at the root of the issue (that and economic inequality).