It's you who is missing the point. At issue is not whether the government or private party can take surveillance photos, it's whether the government can compel (ultimately by force) someone to have their image taken without justification.
The cops were claiming they had to power to demand his picture. Demand as in not take no for an answer. If the police have the power to demand one's picture (e.g. mugshots when arrested), then they have the power to restrain the person to get the picture they want. In such case, grabbing him would not be assault, but force necessary to carry out a lawful order, and he could be arrested for resisting. Is the real issue here becoming clearer?
The real issue was clear all along, poor wording in the description of the case.
It's not that a photograph is an illegal search and seizure, as the article said. If the police had simply left with the pictures they'd already taken, with the man covering his face, then there wouldn't have been an issue. Taking the pictures wasn't illegal. The problem wasn't one of photography.
The problem was that the police arrested a man for not uncovering his face on demand. Take the cameras away and it still would have been illegal to force the man to uncover his face.
The article makes it sound like simply snapping someone's photo is an illegal search and seizure, which is folly and implies all sorts of goofy stuff like unconstitutional security cameras.