Censorship is something governments do. What you're discussing is a business decision Facebook made. They deemed it to be in the best interests of their shareholders not to amplify those peoples opinions. Zuck now regrets that decision, but it was still his decision.
Semantically, you're right of course, but only because linguistically self-censorship is counted as a type of censorship, despite it not depriving anyone of liberties.
For practical purposes though, the kind of censorship that we're concerned with in this conversation can't be done by anyone other than a government or a lunatic with a gun. Companies just don't have any authority over anyone except themselves. They can't deprive you of your ability to speak, only your ability to use their property to do so.
The article says they were "pressured", it doesn't seem to to say how that pressure was applied. To me, it reads as though compliance was not mandated, just requested. Without more info, I suppose it could be taken either way.
If Zuck has a real problem with that, he can sue (as per the SCOTUS ruling on standing vis-a-vis First Amendment protections against government coercion).
He isn't suing, and it's up to the rest of us to make our decisions based on how we feel about that.
Call it what you like, if you can't distinguish between doctors and quacks then you shouldn't be banning people you think are quacks because you aren't qualified to do so.
If i stand up a server and host a website, I get to decide who's allowed to use my server. I don't need to be "qualified", and who would decide what "qualified" means? Should the government be forcing me to host content I find objectionable?
