That information wasn't "already available" - ElonJet was purposely and knowingly working around privacy protections, and they didn't hide it either. That's like guessing your password, getting into your emails and arguing "this information was already publicly available". Or installing a wiretap on your phone and saying "well, that information is publicly available".
No, if you take specific action to override explicit privacy protections, it's not "publicly available".
And the story didn't end with this information being just "available". It continued to a masked black bloc wearing person stalking his car and blocking it and climbing on it. Nobody was hurt, so far - but it's not just "information being available" anymore.
Sharing already available flight tracker information - This is an assassination attempt.