I'm no art historian but as far as I know at the early days of photography it was "under attack" and questioned by painters, many thought that photography could not be art, as it was just a snapshot of what you saw and had not been "filtered" through the mind of the artist as a painting.
Later landscape photography as a genre was particularly questioned, and still is today to some extent, as being too simplistic and trivial from an art perspective.
Personally I'd say that anything the author say is art is art, but what the quality of that art is depends on many factors and is in the eye of the beholder.