"Government censorship" is not redundant. Anyone with a channel can censor their channel. That's just what the word means. Google has a very important channel, so it matters when they censor it. Your yard signage is less important, but "censorship" nevertheless.
It's not about "when is it censorship", because by definition it's "every time". It's about "what's the balance between the owner's rights and the community's rights". While I'm strongly biased in favor of the former, once enough of the community depends on you that you have some of the power of a government, then you accrue some of the matching obligations.