A copy of that discussion is hosted on lemmy.world. In fact, all content from other instances on lemmy.world is in fact just a copy hosted on lemmy.world. That is how federation works. If a post that breaks the laws lemmy.world is subjected to, is federated to lemmy.world, lemmy.world will automatically create a copy of that post and make it available to all its visitors. By law, lemmy.world is hosting illegal content. This is a fubxamental design flaw with Lemmy and Mastoson, or the ActivityPub peotocol, that needs to be adressed by the developers, if instance admins are to be sure that they are not breaking laws by federating.

Technically it is, as someone else mentioned, text is copied on federation, this means is you as an admin need to actively moderate instances you federate with that may cause you issues in a legal standpoint whether correct or not. Facebook etc have rights that means you’re not liable for user content, you as an individual instance admin however would need to fight for those rights.

Sure it’s a rubbish thing they did but I also understand it completely.