My life experience is that there are "several" policemen, and the persons in this video seem and sound to belong to this category, that - whether they do it consciously or not - basically approach people with a hidden desire to satisfy their need to feel they are exercising "power" rather than out of a sincere will to do their job properly. It's a benign and common form of sadism. We cannot know if we would show that ourselves in the same position, so I am not fingerpointing more than strictly necessary here, it's human nature at work. Exercising some form, any form of power might bring out the worse of a man. His mind will "justify" his conduct with laws, and "societal needs", but his inner self is pursuing a different agenda.
I do agree that if the photographer had been "collaborative" the thing would have ended with a nice chat, not out of the sincere desire of the policemen to ascertain the lack of public danger (although they probably manage to convince themselves it is so) but out of the basic subconscious "satisfaction" the policeman had in seeing that he is exercising a form of power.
I have also learned, when stopped by a policeman for a road infraction, that admitting my fault openly and immediately invariably causes the policeman to let me go without any fine. Deep inside the policeman wants the satisfaction to be told he's right, and he's content with that.
I only viewed the initial part of the video. The voice of the policeman clearly gave me the impression that he was playing - in his mind - cat and mice. The way he talks to the photographer, since the very first words, is only "superficially" polite, while sounding to my ears clearly provoking in fact. The policeman thought he had the "power" to behave so and was clearly enjoying the situation IMO thinking he was playing from a safe position.