Defederation doesn’t work against large instances
Access and communication across diverse servers is important, and people depend on it to keep in touch with their friends and audience. But the safety and dignity of vulnerable people is more important; knowingly putting your vulnerable members at risk by placing them within reach of a known-bad-actor server is unconscionable. Defederation is one way to protect your members by putting them out of reach of people on a known-bad server.
Having said that, I think smaller instances defederating from larger ones remains disproportionately painful for the smaller instance, and largely ineffective in changing the behavior of the larger. Ideally the answer is to never let any instance (or small set of instances) become large and dominant, but I don’t know how to achieve that end in the real world.
Other solutions like Mastodon’s “Limit” status may be more effective.
