it is not any abuse or exploit, it is how a social network works. There is no system in which everyone sees everything, as this is literally impossible. There are too many messages. Are languages censorship? If I write something in russian the message wont reach a group of people that do not speak russian. This is what nostr clients do. YOU decide what you want yo see. When you are using any nostr client you are filtering all the messages on the network to get a personalised and usable feed. For example, you filter by kind. When using any social media client we are only getting a small set of kinds like posts, zaps, likes… and muting (not censoring) anything else. Just because it is not relevant for the usecase. I am sorry to tell you this: if the majority of people in a small group do not listen to your messages you just… don’t reach that group, and that’s okay, it is not censorship applied to the whole network. And again, it is an optional and client-specific feature. I do not have it in mine, no matter how many friends block someone I will still see their messages (unless I block them myself)