Great, but if nobody uses the small relays that choose not to ban its not much practical use.  In the end we just have to trust the big servers to not censor.   Nostr  becomes centralised around the big well funded well known servers.  
  Saying '  well its not censorship because  you can always take your freespeech somehwere else'  is neither a technical or philosophical  solution to platform censorship,. Every other platform uses this clause - of course anyone can put their posts elsewhere  eg on Mastadon or Nostr  or twitter if censored by one platform.  But that has its limitations, and those limitations aren't solved with Nostr anymore than they are with Mastadon.