I don't particularly believe it's worth diving into the nuance of it here -- because I'll do a bad job! -- but I should make it clear that I wasn't intending to make any comment about whether the principle is right or wrong (I mean, the UN makes it pretty clear http://www.un.org/en/universal-declaration-human-rights/ :)); I'm merely pointing out that free speech/censorship exist on a spectrum, and our tolerances and interpretations of those principles shift over time. As an example, many democratic nations have decided that there are consequences, enshrined in law, for what they define as hate speech.
I suspect that even in the USA, a country that is extremely passionate about protecting the right to free speech, you'd be pretty hard pressed to argue that sharing pirated content (... at the "less objectionable" end of the spectrum ;)) is an expression of free speech. As the content becomes more objectionable, that argument becomes more difficult.
I'm using "objectionable content" as an example here to simplify the argument; I'll freely admit that what scares me is the distortion of the principle of free speech by (as the sibling comment points out) bad actors. I don't know that I have the education or skillset to discuss that problem effectively, but it is an issue that is beginning to have widespread societal impacts.
That aside, the real point is that solving the problem of centralization vs. decentralization does not make the choice of totalitarianism vs. anarchism, or determine/enforce the behaviours we determine to be socially acceptable on whichever platform we use. The technical underpinnings may favour one end of the spectrum or the other, but do not replace a genuine, social discussion about the governance of our social networks -- whether we replace the current batch or not.