Asshats are not mannered people, by definition. I think the solution for this comes from a web of trust filter over top of the matches of the feed. IE: if the #plebchain hashtag appears in an event, you could have it ignore it unless it's 1, 2, 3, 4, or whatever number of degrees of separation from your follow list (follows of follows of follows linkage). I think @jack talked about this in his big article he posted back in april or whenever it was - that building user controlled filter algorithms is critical to Nostr.