The fact that Facebook seems to be genuinely surprised by this response tells me everything I need to know about how they regard their users. They see them the same way an entomologist sees bugs - something to be cataloged and experimented on but not worthy of the respect one normally gives other human beings.
And how can this surprise you? Have you ever heard anything at all about Facebook respecting the privacy of its users? In fact, again and again and again Facebook ends up in the news with an anti-privacy scandal on its hands.
I am not saying that running social experiments on random people is a great idea (though it is funny), I am saying this is a 'no biggie' because it is neither surprising nor out of line with previous actions. That doesn't make it right, but anyone with half a brain should have seen it coming five years ago, and stopped using social media platforms 4 years ago. The only people who need to have these accounts are the marketeers. The rest will get much better 'social' results using 1) a phone and 2) mouth + ears.
I suppose since Facebook is owned and run by an immature child billionaire that I shouldn't be surprised.
And yet you appear to be. Facebook is run by a greedy thief, and you expect non-greedy-thief behavior. That is inconsistent.