Without the need to agree or disagree with the ruling itself (which I cannot read about, as the article is behind a paywall, and I expect that the ruling is more nuanced than what the clickbait title suggests), the fact that a person was condemned for saying something for some reason (provocation to hate I would assume) does not mean that a mastodon server would be liable for relaying the information. Actually, politicians get condemned on a regular basis for diffamation or hate speech, but I never heard of any TV channel or newspaper being sued for having reported on the discourse of said politicians.
I have to say that I expected a bit more, as you mentioned "most content on the internet".