how to block meta from mastodon

That's disingenuous. It's not like Meta is some unknown party here with a clean reputation. They have a history, one that repeatedly shows they couldn't care less for the fundamental freedoms of the fediverse. Just like in society, for us to build free platforms where everyone is welcome, we must paradoxically not tolerate those that wish to wield the freedom of the platform against itself.

Ever heard of Mastodon blocklists? I mean defederation has been happening for a while.

But I think that's fine. Instances should have every right to block instances that they disagree with.

Except Meta by it's nature will aim towards Centralization. They're contradictive to the concept. It doesn't even take much thought to see the issue here.

Also as app_priori pointed out, Almost every instance already has a list of defederated instances.

This is like starting to date a known habitual cheater