Chomsky is being an asinine troll if he’s comparing “Western censorship” to anything that takes place in a country like Russia or China.
In a totalitarian state, like those two, you can be thrown into the 21st-century version of a gulag simply for possessing government-critical material, or attending a protest with a blank sign. Access to any websites with dissenting information is severely curtailed behind a “firewall.” Independent thought is crushed — you must parrot the party line in order to advance or even to hold a modest position like a teacher. (Anti-war teachers were ratted out by their students in Russia.)
In the West, what contrarians hyperbolically describe as “censorship” is usually just content organization. If you submit a right-wing meme to politicsTOO (an explicitly liberal stream), then I’m going to unfeature it. But I would feature the same meme if submitted to a different stream with no stated viewpoint. Also: you can turn around and submit the same meme to conservatives, Real_Politics, or the main politics stream and find a receptive and likely even larger audience. I don’t try to flood the Firearm_Friendly stream with pro-gun control content, because that would ruin that stream’s editorial independence. If you insist on submitting cat memes to the dogs stream, or vice-versa, then you’ll encounter the same problem. Your content will be unfeatured, because it doesn’t belong.
Now if you show up to Imgflip ranting about “death to the Jews,” or whatever, then the first global mod who finds you is going to nuke your account. But you can post all sorts of violently bigoted thuggery on Stormfront or 8kun or any other “free speech” hellhole of the internet. You won’t be stomped on by federal jackboots for owning a copy of Mein Kampf. But if you actually go out there and start assaulting and killing Jews — yes, of course you’ll be arrested. Because doing that to anyone is illegal.