Nostr alone won't protect you from government censorship because your government can arrest you for breaking the law, regardless of what platform or protocol you use.
Nostr does protect you from corporate censorship, however.

This is more than enough to make Nostr useful as a censorship-resistant protocol. While there are some limits to what (liberal) governments censor, there is no limit to what platform owners can censor, and they do arbitrarily enforce stupid rules.
They have the right to do so, they own the server.
We have the right not to filter what we write and read trough the whims of a few rich individuals and Nostr is the way to exercise that right.