Proof that it was censored by the United States government is what decides if it’s legal censorship.

It isn’t obviously, it serves the exact purpose of conducting censorship on behalf of the regime without any hard govt power being employed. The legality isn’t what I’m concerned with — if that were the problem we would be able to solve this through courts.

Well, that's my point - if people are that aligned with an ideology separate from any specific pressure, then their actions are their own and they're not spies nor are they connected with US intelligence agencies.