You mean its impossible? By which mechanism? Clients are centralized and can hide whatever content they wish.
Relays can block whoever they wish as well.
Compare it to Bitcoin where you pay fee and network doesnt know nor care whats the purpose.
Imagine the worst stuff here. Dont tell me it wouldnt get hidden (I dont mean user blocking)
Markets of relays and clients are open. If users are not satisfied with some kind of automatic blocking introduced by a relay or a client, they will move to another relay or client, preserving their networks and data. If there wouldn't be such an option, it would be censorship. For example, you can't move to another vendor and get YouTube or twitter without their blocking, that is why those platforms are with censorship. You can move to YouTube's competitor, but you would lose your YouTube network and data
