[giaour]

Why not just ban the accounts of people you want to exclude and not open account registration to the public? The system you're proposing presupposes accounts, login, and some form of external trust anchor; I guess you can use the NFT issuer as the trust anchor, but that just pushes the problem of deciding who gets in from account registration to NFT issuance. Users would be able to delete/recreate their accounts without re-proving their in-group status, but that's the only advantage I'm seeing for using NFTs in this system.