Image manipulation is inherent in photography. There is no unmanipulated image.
This has been true for more than 150 years. Before Photoshop. Before enlargers. Even before negatives.
The first manipulation occurs when the photographer frames the subject in the viewfinder, LCD or ground glass. A selection occurs. Things in a scene are included and excluded by choice or accident.
Manipulation continues with focus. We render some objects sharp, and others blurry. This is also a decision by the photographer.
Another manipulation occurs with the choice and control of exposure. Adjusting shutter speed and f/stop includes some tones in the sensitivity range of the film or sensor, and excludes a lot else. We make a selection.
This is just the beginning. Every step of image creation that requires a decision, an adjustment, or a selection - from the initial composition and capture to the final output onto paper, screen or some other kind of medium - is a manipulation of the "objective reality" that is in front of the lens.
The purpose of the photograph dictates how much manipulation is ethical, acceptable, or tolerated. Journalism has no use for photographs that clone in or remove graphic elements. But cloning is commonplace in advertising. Fine art photography, which is about expression, permits the greatest amount of latitude. What matters is the artist's impression and visualization. The image expresses this, or rather, the artist expresses this through the image.
Alain Briot writes about this topic in a lengthy article that recently appeared in the Luminous Landscape website.
He begins by observing that photographic artists (as distinguished from journalists, documentarians, or commercial photographers)
... manipulate because manipulation is how we express our artistic license. In
other words, manipulation is a fundamental aspect of art. In fact, we could say
that manipulation is art, or conversely, that art is manipulation.
Reading the full article is a worthwhile investment of time. Thoughtfully reflecting upon it is even better.