Photojournalism and commercial photography are two completely different beasts. Without getting into any theoretical arguments about what is photographic truth, photojournalism tries to convey the facts of an event where as commercial photography want to convey an idea. Reality and truth don't matter. After over a decade in this business, more and more I think of it as image making through photographic processes.
And for the record every, and I mean EVERY photo you see in an ad, editorial spread, billboard etc... has been manipulated. This has been true since the dawn of photography. Even Ansel Adams would quite literally move boulders to get the shot he wanted. How is manipulating the scene before hand any different than doing it after.