The words "childish" and "annoying" are dangerous to throw around here, because it creates a culture of non-acceptance and weirdness for someone who is doing nothing wrong. This is how liberties erode.
I guess he's just "exercising his liberties", but that doesn't make it elaborate. Unless pointing out that people don't like awkwardness is all of sudden an elaborate statement.
The responses are fascinating. A lot of people quick to anger. Many more people who have some — I'm assuming, although I'm no expert on the law in the particular area — false impression that they cannot be filmed without their permission. An alarming number of people who are prepared to call 911 over such a trivial matter.
I've never seen anything quite like this before.
How well would you work if I stood quite close to you, behind you, looking over your shoulder. "Ignore me! I'm just observing. Pretend I'm not here." I suspect many people would find that disturbing in a deep and hard to define way.
He's not doing anything illegal, but that doesn't mean he's not doing anything wrong. He is being rude, and he is confrontational.
Just because that is your approach, doesn't mean that it's true for him.