I mean, the entire domain name infrastructure is set up so that someone along the path can revoke registrations, all the way up to ICANN itself.

IME you're much more likely to be banned by the registrar than the registry itself. Registries want people to use their TLDs, so they're not going to reject post-registration unless you've changed how you're using the TLD and it's violating the rules they originally laid down. Registrars are much more consumer facing and will act accordingly - i.e. GoDaddy banning Gab.