So... if you don't want your posts to be used... simply don't post? Post in a place that has guarantees against such things? I mean, kind of hard to get mad about someone using something we all collectively just toss into the void...
The issue is not that they imported the content, that's how federation works, but how they did. Fediverse is built on consent, opt-in/opt-out is the one of the key aspects that makes it opposite of corporate social media. Apparently, they are so incompetent that they imported DMs which are between 2 users and not in the public timeline.