It is the ability of communities to choose not to federate with anyone else which gives Mastodon its strength.

There are zero mature federated ecosystems where this statement is true. While the freedom to (dis)associate is foundational to federated systems as an abuse management tool, it's existentially dangerous when deployed as an idealogical weapon or negotiating lever.

• The internet is federated, but you don't see tier 1 ISPs de-peering each other over arguments on social media.
• Email (which IS a great analogy... exactly because of the precedent for combatting abuse at scale) is federated, and you don't see major providers blackholing major providers.
• Telephone networks and the banking system are both federated, and generally major players don't de-peer other major players within established ecosystems.

In all these cases, there were phases where the network was immature and these squabbles did happen. But players who isolated themselves lost relevance, and eventually the value of connecting to the wider network (with all of the challenges and opportunities that brings), became greater than the value of winning any other dispute.

This idea that de-peering everyone you don't like is normal and how marginalized communities get protected is only popular right now for a short while because the fediverse only just barely matters at all, and almost everyone is willing to disrupt the health of the network is truly painful ways for any reason or no reason. If the fediverse doesn't kill itself with infighting, the groups that find ways to address their disputes while remaining connected will come to form the fediverse that matters.

Of course, anyone who disagrees can defederate with anyone and everyone if they wish. But in so doing, they limit their own reach and relevance until eventually they're left alone talking to themselves on a fedi-desert-island. I get marginalized communities not wanting to deal with the hassle of a growing network, but getting marginalized stories heard is one of the key ways to improve things going forward and defederate-first-ask-questions-later doesn't help there.