The original post this all began with was Eugen encouraging instance owners to block any Gab instances, because Gab was looking at moving onto the Fediverse.
It is ok for instance owners to defederate as they see fit!
Some defederated mastodon.social because they didn't like very large instances, and that was their choice.
No one talked about it impinging on Eugen's freedom of speech, or the freedom of speech of mastodon.social's members, because it didn't.