In reference to the above statement and taking it literally, I would disagree that documentaries are fictional forms. But with what it could imply - I agree, which is what I will be discussing.
The purpose of a documentary is to inform viewers and show them various issues that confront us in our everyday lives, or that can give us knowledge of things we don't necessarily know about. The definition of "documentary" is:.
"Documentaries present facts objectively without editorialising or inserting fictional matter, as in a book or film.".
This definition in itself contradicts what Wiseman was suggesting. However, there is evidence that this isn't always the case in all documentaries. Because producers have full control of what is shown, they can manipulate a viewers perception of what they are watching on screen or what is been portrayed. Editing techniques and staging certain events can achieve this and may not necessarily be factual therefore making what is shown fictional and subject to authenticity.
Nanook of the North by Robert J. Flaherty wasn't originally intended as a documentary because this genre hadn't been defined at the time that it was made. But many people see it as informative of Eskimo life, which is something they probably never knew of before and so was deemed a film that documented an aspect of life towards the most northern parts of Canada. The scene of the family climbing out of the kayak is obviously achieved using editing because it would've been impossible to do for real but because it wasn't intended as a documentary originally, it cannot be said that it is used to mislead people.
Although there are two arguments for Nanook of the North, some documentaries are purely made just to inform people of real-life events. The "9/11" documentary was supposed to be about the New York Fire Department, but because of the dramatic situation that happened on September 11th, it became something else.