You probably heard that the Twitter-account of Donald Trump recently got compromised by the owners of the platform. I don't want to engage in any political discussions, but the main flaw with this is the violation of freedom of speech.
No its not! In my opinion, Twitter should have banned Trump a long time ago. He has been posting dangerous content for way too long. Freedom of speech only means that you can share your ideas. It doesn't mean that anyone has to give you a platform to do so, and it doesn't mean that you can threaten people.
There are issues with Twitter having so much power to silence people. For example, they also recently banned Sci-Hub. Similarly other GAFAMS have already hurt LGBT communities and other minorities with excessive bans. Federation does solve a lot of theses issues. Someone mostly disliked like trump, would be booted of most instances, while Sci-Hub, or LGBT communities, would be able to find many willing instances to host their content.
The idea that the Fediverse promotes the completely stupid "Free speech" view of the alt-right where anyone can say anything to anyone without any consequence is absolutely false. What the Fediverse enables is the possibility to have the rules of what is accepted be much more democratic.