That's a casual reductionist definition of censorship.
Community edited wiki != Censorship
Centrally administered information channels == Censorship
The state has equal power as citizens to make edits. Meanwhile the state has exclusive power to shut down network access, persecute people for publishing edits or providing access to censored information, chilling effects, etc. Pretty big difference.
That really depends on the community and the nature of their editing. What if Westboro Baptist Church members decided to do nothing but en-masse gradually edit their Wikipedia page? You would probably categorize their actions as an attempt at propaganda and censorship. (On a short term, of course.) It ultimately wouldn't work, since they are such a small group. However, if a large enough segment of the populace decided on a program like this, which also included an infiltration of the higher-level of Wikipedia's organization, such a program would probably work.
Content addressing means that all versions of the page remain available so long as one node hosts it, and they are easily differentiated.
On the internet 1000 voices don't speak 1000 times louder than one, it would be relatively easy for a small group to widely advertise that there is a discrepancy.
Effective propaganda would only be possible where any contradictions are unable to provide evidence, causing an appeal to authority to become one of the most viable means of resolving the dispute. This is where the majority - but not all - of our current propaganda sits.
IPFS would help. It wouldn't solve disinformation but it would tidy up the game.
Yes. A lie can run round the world before the truth has got its boots on.
For the second case, this is why I talk about the nature of effective propaganda. Evidence is the only reliable way to fight against an authority, as the larger group would be significantly less able to censor evidence they are forced to use unverifiable propaganda - this is much less effective for them.
Community edited wiki != Censorship
Centrally administered information channels == Censorship
The state has equal power as citizens to make edits. Meanwhile the state has exclusive power to shut down network access, persecute people for publishing edits or providing access to censored information, chilling effects, etc. Pretty big difference.