Then I would ask "don't raise your hands, but when dealing with your kids, have any of you ever acted in a way wasn't captured on camera?"
I don't mean beating or physical abuse or anything that horrible, and everyone knew it. Combine young tired kids with a cranky, tired adult, and it's almost guaranteed that the adult will have had at least one rage meltdown.
They probably only yelled and ranted. But they probably looked like a monster doing it.
How quickly would such an image or film go viral? And how condemned would the person be?
We are all foibly humans, we all have moments that we regret or that fill us with shame. And we're all glad they weren't recorded for posterity.
Privacy isn't about protecting your best face, your public face. It's about protecting all of your faces, all of your moods, your knowledge, your relationships, etc.
We have free speech, but do we have freedom from judgementalism? Until we do, we all need privacy.
A less biological, more modern concern, is that a potentially super-intelligent actor (e.g. an ML team dedicated to finding human weakness and exploiting it, like marketing depts do) could find out things about me that even I didn't know and use it against me.
In the modern world complete paranoia and distrust in is the only strategy with guaranteed sucess which respects our drive to survive. Mass-manipulation of elections is a symptom of the disease.
I’d be shocked if most people would be ok with public disclosure of every inconsiderate, off-color, or poorly worded joke you’ve ever made in private. That’s leaving aside things like intimate conversations with a spouse/SO, etc.
That said, I wouldn’t be using a service like this to get there, but I do value the ability to use a privacy-focused messaging app in my day-to-day life.
How you want your doctor to tell you that you've got gonorrhea: in a private conversation in their office, or through shouting it at you in the waiting room?
Whistleblowers, human rights activists, people in abusive or dangerous living situations they can’t immediately escape, sexual assault victims seeking support in private, a well known person who has personal issue they want to keep to themselves.
If you stand to lose a lot by being identified, then you’re a use case.