It does not follow that e.g. if your day job is singing or acting, that you want people to interrupt you and take photos when you are eating in a restaurant, or discuss your relationships in a tabloid. Many would view it as an unfortunate side-effect of the job, or worse.
It is somewhat unfortunate, but it's also well-understood, as you start working to get into these spaces you know it's a significant risk especially if you're aiming for the more popular kind of public act[0].
And that's not a recent phenomenon either, public performers have had significantly lowered expectations of privacy… ever since the concept has existed really.
What I mean to say is: if you're an artist, you're aware that this shit is a risk, and you can act to mitigate it, and it's a pain and tiring but at least it's that. And if you know dealing is not an option, you take a different path or take care to hide your identity early on (à la Banksy) or use some other means of separating a public persona and a more discrete private one.
If you're a rando, the expectation is not that you're going to be made "famous" for mundane actions, it's not a side-effect or your career and benefits, and you're basically hosed.
[0] Dave Chambers / Blindboy Boatclub can probably expect less intrusiveness into their private life and actions than Beyonce or Chris Pratt
But I don't think there's any slippery slope there. People who aggressively court public attention should expect to receive public attention. People who don't generally shouldn't. (The exception for me being people who willfully harm others.)
Compare that to Michael Jackson or Britney Spears (or any number of artists up and down the sliding scale of celebrity). Sure, they wanted to engage with the world through their music and their art, but I don't think they defined themselves as people solely through their craft, and I think (opinion) it should have been their right to determine on what channels they publicly engaged with the world. Not legally, but as a matter of common decency.
Or does everyone who e.g. publishes open source software deserve to be doxxed?
Michael Jackson and Britney Spears put themselves front and center. But J.D. Salinger, for example, didn't. I think the former don't really get to complain that people are interested in the product they are selling. Scientists are another good example here. Carl Sagan clearly sought celebrity (and used it very well). Plenty of Nobel Prize winners didn't.
I also agree "wanting to engage" is an important part of it. Steve Bannon clearly likes being in the public eye, while Stephen Miller doesn't. But both of them are seeking to shape the lives of millions, and so to my mind are legitimate focuses of public attention.
I think the core of my question is this. You agree we have a right to choose whether we want to engage with the public. Do we have a fine-grained right to engage in one area of life, but not others?
Historically, I think this has been the case (e.g. keeping family out of politics), but I think the line is blurring over time, and I'm not sure that's a good thing.
I think keeping family out of politics is not so much about keeping one area of the public figure's life private as allowing the family members to keep their own lives private. Maybe that line is blurring, but I'm not sure the public is entirely to blame. Politicians often use families as props and even shields, as when the wife literally stands by a philandering politician in the apology press conference. And the Trump administration has actively involved the whole family in governing. So I'm not sure I'd lay changes here at the feet of social media.
I would only add that in some cases (some of them notable today) people have nothing to contribute besides a desire for public attention. Public attention is not a right or a tap that can be turned on at will, and I don't care to give it to dull, uninteresting and shallow people.