Yes and no. The people still have the voice, you're not preventing them from talking to other people, you're just preventing them from accessing your instance.

Centralized websites like Facebook, Twitter, whatever. That would be censorship if they remove somebody's voice.

Decentralized instances, are closer to private communities. They're focused, and they create curated viewpoints.

If the federated universe gets dominated by one or two powerful instances, then yes it would be censorship, but if people are using it at a decentralized fashion: it's just communities expressing preferences.

"Boo hoo, people aren't being forced to put up with my stupid shit, waah!"

Yes, it is, but I'm not a Libertarian - some censorship is good. Fascists, trolls, and child pornographers deserve to be censored.

Get fucked.

It's our right to live in a safe environment without Nazi fucks.

You have an entitlement to speech, you're not required to be heard or listened to by me.

lolno

You can say whatever the fuck you want, but other people aren't obliged to listen to it or pass it on.

Talk to the hand.

People not wanting to engage with other people is not censorship. Nobody is entitled to someone else's attention.

Not really. These aren't monetized sites, but just individuals inviting guests to use their instance over self hosting their own, and there's other instances people can move to.

Each instance is better seen as individual forums than a reddit type centralized site. Some forums allows cross account logins, and some you have to create another account. And defederation doesn't cause that instance to cease to exist like banning a community or subreddit does.

You could also say it's a form of tribalism

In many cases it is simply censorship.