Well… They are of course right about the fact that these sorts of decentralized systems don’t have a lot of privacy. It’s necessary to make most everything available to most everyone to be able to keep the system synchronized.

So stuff like Meta being able to profile you based on statistical demographic analysis basically can’t be stopped.

It seems to me, the dangers are more like…

Meta will do the usual rage baiting on its own servers, which means that their upvotes will reflect that, and those posts will be pushed to federated instances. This will almost certainly pollute the system with tons of stupid bullshit, and will basically necessitate defederating.

It’ll bring in a ton of, pardon the word, normies. Facebook became unsavory when your racist uncle started posting terrible memes, and his memes will be pushed to your Mastodon feed. This will basically necessitate defederating.

Your posts will be pushed to Meta servers, which means your racist uncle will start commenting on them. This will basically necessitate defederating.

Then yes there’s EEE danger. Hopefully the Mastodon developers will resist that. On the plus side, if Meta does try to invade Lemmy, I’m pretty confident the Lemmy developers won’t give them the time of day.