Say there are a dozen large instances that hold 80% of the Fedi population. Will your medium-sized server with a growing community actually be able to defederate from any of them?
When a major instance is made of 75% regular people and 25% Nazis, but account for 7% of the total Fedi population, you can’t threaten to defederate from them unless one or more of the other 11 major instances also threaten to do so. Your instance would stand to lose way more than the offending major instance would, because the users on your instance depend on a lot of non-problematic traffic from the major instance for their feed, but not the other way around.
In short, your threat of defederation has zero power over a major instance.
Using defederation as a tool to enforce social norms only works among peers who need each other equally. We need better tools to deal with bad actors on very large instances.
