This whole article is about private information. The flight data is, as enough people already told you, not private information. For good reason.
Social Security Numbers used to be treated as quasi public data too.
Not really. There is no guarantee that Elon is on the plane. He could loan it to a friend or one of his companies VPs. The plane could be at it's home airport, fly to another airport to pick Elon up, fly to a third airport to drop him off then return to the home airport. Elon would have been on only one of the three legs.
Retract this statement, now that this crowdsourced data was used to stalk Elon's family.