I don't think freedom of speech is equal to freedom of lies, If the truth is covered up by cracking down on lies, it cannot be called freedom of speech.
The question is if Twitter is a platform or a publisher. If they are a publisher they have the right to have editorial review, but then they also are liable for every post made just as the NY Times is liable to anything they publish in their paper.
If on the other hand they are a platform they can have lines that cannot be crossed, just as a track has lines for the lanes or a basketball court has lines showing what is out of bounds. The lines need to be transparent to all and you can blow the whistle if someone fouls another person. If you are a platform you can referee, you cannot decide who can and cannot play.
What Twitter has done and the evidence is now coming out is that they created algorithms that allowed them to "turn up the volume" on posts they liked. They could have phony bots subscribing and liking and commenting which gave those posts much more prominence and made them appear much more popular. Not only so but they could turn down the volume on posts they didn't like. They could make it seem these posts had far fewer subscribers, fewer likes and fewer views. Since people have a financial interest in this you can call that robbery and no doubt if the evidence comes out there will be lawsuits (the sequel to the movie "There will be blood").
This explains the meltdown when he bought the company because all the employees knew what they were doing. They knew they were taking the weirdest 1% of the world and making them appear to be 20% and taking those who represent 65% of the world and making it appear they represent 35%. They knew they could influence elections, and push their corrupt agenda and now it will all be exposed.