Assumption 1: Meta / Mark Z are objectively untrustworthy

Assumption 2: The Fediverse is a threat to the entire internet advertising machine

Assumption 3: Threads will be a hospitable place for right wing hatemongers. Therefore, federating with it exposes our most vulnerable users and communities to a deluge of (often invisible) hate and harassment.

Assumption 4: Most of the ways that they could use their billions of users and army of programmers to slowly choke us off would go through federation

I think if you believe all four of those assumptions defederation is the clear choice

https://ploum.net/2023-06-23-how-to-kill-decentralised-networks.html

I know we all dream of having all our friends and family on the Fediverse so we can avoid proprietary networks completely. But the Fediverse is not looking for market dominance or profit. The Fediverse is not looking for growth. It is offering a place for freedom. People joining the Fediverse are those looking for freedom. If people are not ready or are not looking for freedom, that’s fine. They have the right to stay on proprietary platforms. We should not force them into the Fediverse. We should not try to include as many people as we can at all cost. We should be honest and ensure people join the Fediverse because they share some of the values behind it.