By my standards of social behavior that dude is a fucking creep and (years ago) I would have tried to go over and confront him, and get his license plate, and maybe even call the cops on him. I know it's not illegal to photo/film people in public, but (again, by my personal standards of social decency) this guy's behavior is hella creepy.
Of course, the answer is: he's a millennial and (to him) what he's doing is perfectly normal. Everybody is a tactless voyeur now, and all your photons/base belong to us. Anything worth looking at is already getting mobbed by the panopticon.
(My solution is to buy some land in the woods, cover it with surveillance gear and build large, intimidating robots to patrol the fence. But that won't scale.)
The problem is, our whole civilization is that guy: the advertisers, the NSA, the crooks and creeps, all of them are after your data and have a head start.
We can't put the tech/genie back in the bottle (I don't believe we can.) So that leaves us with creating a kinder, gentler dystopian hell.