Part of fair and open decentralized social networks is that everyone is equally allowed to be involved. May not like him, but disallowing someone access to the protocol goes against the entire ethos of the system. Individuals have the right to block them from their view or relays but blocking someone at a protocol level is monopolizing control of access the same way mainstream social platforms do. 

 Yes I know, if you know me you should know I’m just kidding about here.
But seriously I would prefer that he doesn’t use Nostr, but each to their own.