'Public' online spaces don't carry speech, rights
Rant all you want in a public park. A police officer generally won't eject you for your remarks alone, however unpopular or provocative.
Say it on the Internet, and you'll find that free speech and other constitutional rights are anything but guaranteed.
Companies in charge of seemingly public spaces online wipe out content that's controversial but otherwise legal. Service providers write their own rules for users worldwide and set foreign policy when they cooperate with regimes like China. They serve as prosecutor, judge and jury in handling disputes behind closed doors.