Some good counterpoints. But you're suggesting more people would be okay with 'PI following them' hypothetical than GP suggests—simply with the knowledge that others are subject to the same degree of surveillance?
I'm not so sure that counterpoint in particular holds. I think to say the "number of people that are going to be okay with that will [still] plummet" is an understatement. I'd go so far as to say no one, at least no rational person, would be okay with a "record [of] who you talk to, when, how long, where you go, what you do, what you say, when you sleep", etc., just because of the scale.
Let me focus it from a slightly different side: my believe - from observing the world around me - is that physical privacy violation is perceived differently from a software one because of the side-effects: you gaze out of your window and see the same car with some guy in it parked there, you see the same car following you when you are going to the mall etc. There is some similar side-effect with online tracking, which is the typical "ad in my Instagram feed for something I searched for last week in Google", and there are people that are "scared" by this. But since it's just about buying things, well hey I might actually tap on that Instagram ad!
I see some success by telling people "what if was our government doing the same thing to us, even by extorting private companies? what if that same government, or the next one, just hates you for whatever reason?"