EDIT: (At least, that's how it works in the US. Other nations, other laws.)
Feel free to argue that Facebook should be allowed to censor others. But it is still censorship.
It is perfectly possible for someone to both think that Facebooks actions should be allowed, and are also censorship at the same time.
It would have a pretty small effect on other people's ability to engage in speech. But it is an effect none the less.
If you owned a huge amount of property, though, then this would be a larger amount of censorship.
It absolutely has something to do with the general concept of freedom of speech, actually.
Freedom of speech is a concept, not just a law.
Either way, I think people have also a wrong idea of what censorship is. If I tell you can't take a shit in the middle of my living room and you claim that I'm censoring you, then maybe you should reconsider your logic and definition of censoring. This is basically the same.
There's no one who would advocate complete and total freedom of speech in every arena. Whether it's social, legal or self censorship, the question isn't about whether a line exists, it's where we place it.
I'm not changing what "freedom of speech means". I'm telling you that freedom of speech doesn't come with extra rights to give you the ability to disperse your thoughts and Facebook is also well within its own freedom of speech rights (as a Corporate personhood) to enforce whatever content rules they want.
Either way, I'm not even trying to argue here. You believe this is censorship. Fine. I respect that and really don't see that as an irrational thought at all. There's some sound reasoning around your idea that this is censorship. I just think that trying to create blanket definitions for "censorship" or "freedom of speech" is an easy escape to allow people to behave like shit. That's what I think. Totally a personal opinion, though.