Every one of those items, does, in fact affect the elements in the photo. Your criteria of what defines a photo is as arbitrary as anyone else's set of criteria.
Normally I'd agree: my opinion, if that is what we're talking about, isn't worth more than anyone else's.
But I am a bit surprised by the last round of discussion that I've been involved in. I had assumed that it would be easy to establish a small set of parameters that could be applied to one's thinking that in turn would make it easy to evaluate if a photo is indeed depicting some form of objective truth.
The example of the forensic photographer is a good one: he or she enters a small room with a dead body on a bed. There are red stains on the sheets, a few crumpled dollar bills and a bloody knife. Additionally, on a side table there is a small orange, translucent canister that is half full of pinkish pills.
This scene can be documented with a series of images using a 24mm lens. You could also use a 35mm or a 50mm. You can shoot digital or film. You can use ISO200, 400 or 800 film.
When the photographer develops the images they realise they are more detective than photographer, so they didn't use exposure compensation in the all white apartment and on the white sheets, so they came out a bit dark. In the development process he or she pushes the exposure a bit to make a brighter image. Alright. A valid photo of the scene.
Now, I am hoping it's clear to everyone that in terms of "evidence" it's not OK to clone out the looks-like-blood-stains on the sheets. You also can't remove the knife because it's disturbing, or the pills because you prefer the "cleaner lines" of the scene without them. You also shouldn't go in with a local brush targeting the orange canister or the pinkish pills and change the hues around or make just that small area more or less saturated.
It would be deeply worrying if at least this part isn't CLEAR to everyone. Did you remove the knife from the bed? Did you remove that strand of hair on the cheek? Did you remove the guy next to Hitler in this photo? Did you just add a lynx to your backyard early dawn garden shot?
In terms of local vs global adjustments: our eyes are very good at compensating, so if we look at an image that is very saturated, we can tune it down in our heads back to 'memory color' territory. Same with desaturated images. But if someone takes a photo of an impressive sky and then feel it would be even more impactful with more saturation and then make a local adjustment leaving a "normal" foreground and a "burning" sky, that actually tricks people. Because since the foreground element is normal, a conclusion can be drawn that the sky is real. "WOW, this was an AMAZING evening!! Great capture!!"
Anyway, from other discussions I've had on the topic, I know I'm not alone in thinking like this.
To tie all of this back to the title of the thread before exiting: a photo is objective, an image is subjective. Both are valid on their own terms. But taking something subjective and calling it objective is potentially a lie. Art is good and desirable, but you don't want to take fiction and sell it as truth.