For several years I helped to moderate a huge International Relations discussion forum with 15,000 members from all over the world. Debates were vicious and impassioned as Islamists, Communists, Democrats, Feminists and even one Monarchist hammered out their arguments. It was fun and insightful to read all these diverging world views, but some members were problematic and used the anonymity of the forum to personally insult others. We moderators had to balance our commitment to free political debate with the pragmatic concern that the attention-seeking trolls could drag the discussion irreversibly into the gutter if we did not censor them.
When we did choose to censor and control the debates, we were abused for being anti-freedom.
This was, however, an absurd complaint. The website running these forums, Orkut, allowed any member to create a new forum. The creator was called the 'owner', and Orkut gave them dictatorial control over its content. Any post could be deleted, any member could be banned.
Gradually we realised that each forum could be considered the private property of the owner. This was practically true since Orkut had invested great power in the owner position. Fighting the owner was pointless because, beyond actually hacking the site, the owner was in a position of unassailable power and would not be removed, even by a democratic election of the members.
So the owner of the forum was, like the journalist who runs her blog, the owner of private property. As such, some of us began to argue that the owner is entitled to control debate on her own property. This is not against freedom of speech, since the banned or censored members can simply continue their debate on another forum.
This is a critical point. The American First Amendment reads:
Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.
Their freedom of speech is not curtailed simply because I deny them my particular property. They can continue arguing their world view on their own property.
This applies to literal property, and to online discussion forums and blog comment sections, but also to newspapers and other privately-owned media. Sometimes people complain about censorship in privately-owned newspapers, since the newspapers refuse to give everyone an equal platform.
This is silly. Here in Ireland no mainstream newspaper would give a tiny neo-Nazi movement a platform to express their views. There need be no concern over this; newspapers don't need to publicise every crackpot theory they come across.
Of real concern are laws created by government which apply to all debate, and not just that going on in one's own property, for these really do curtail free speech. Ireland's recently-enacted blasphemy law is an example. There is no escape from that, no safe retreat to one's own property, so that really does inhibit our freedom.