Pushing an agenda of literal chaos and death through theories like "it's only the flu" or "mask = oppression" is getting actual people killed, right now, by the thousands. Of course the devil is always in the details and the fuzzy lines.
https://www.theatlantic.com/national/archive/2012/11/its-tim...
Encouraging people to violate mask orders would fit this definition.
Simply advocating that people violate mask orders doesn't pass the imminence test.
Well, look at what happened with Alex Jones and his Sandy Hook theories.
If they cause measurable harm to others, then yes media companies have a responsibility censure people on their platforms who spread conspiracy theories.
The conspiracy theorist's right to free speech doesn't mean Twitter is obligated to carry their speech, either.
If you dislike this your best available remedies are 1) find a service who wants your business, or if none such exists, 2) start your own social media service, or to "solve" the problem for good, 3) engineer the existence of government-operated social media services such that law mandates all citizens have unfettered free speech on the service
As far as President Trump goes, Twitter has had to make policy exceptions in order to ensure his continued access to the service, AND legal proceedings have also resulted in rulings that govern his specific use of the service (for example, he's technically not allowed to block citizens.) As such it's not especially useful to look at Trump's experience on Twitter and try to generalize it to anyone else.
Maybe it's not just freedom lovers making use of their God-given right to free expression, or whatever.
They are going further than this on also removing many accounts from search, but given the many bad apples, I am unsurprised they're hiding the bunch.