Saying "Twitter and Facebook are private, they do what they want at home" is a form of neo-feudalism. "The Lord does what he wants on the land where I live and which I cultivate". But feudalism was the middle ages. We have evolved since then.
Some don't realize the arbitrariness of the decision, and what it means for democracy that a platform that acts as an intermediary for hundreds of millions of people to talk to each other decides on its own who can talk there? A domino has fallen which will force social networks to justify keeping this or that account open, letting this or that thing be said, and in order not to take any risks, to censor them too. Where do dominoes stop?
The craziest thing is that those who find it normal seem to think that it is either to leave this power to the platforms without counter-power, or to let everything be said. But oh, didn't we invent something modern called "justice"?