"Art" used to advance political, social, or other idealogies is really nothing new, and it shouldn't be surprising that new technology is used to make "better fakes." If one goes back to the time when the "news" was spread by broadsides, posters, or other means, when woodcuts were the standard way of printing pictures, the same sort of thing is seen.
When Erhard Schoen published his Devil with Bagpipe, somewhere around 1535, with the "pope*" as the bagpipe, it was immediately picked up by the opposition, digitally edited if you will, and returned in opposing pamphlets as "The Devil and Martin Luther." (Schoen was a "hard core" Lutheran, so it's not hard to tell which was the original version of the title, although people still debate it. The same picture, or one of several "altered" versions, can also be found by the later title on the web.)
*Schoen had probably never seen the pope, so he may have used a "local" priest for his model???
Most professional photographers do quite a lot of editing of nearly all pictures that are "published." It would, in fact, be rather cruel to release many photos without some "improvement." We don't realize how many pimples, warts, and wrinkles we have until they stare back at us from a "stark" photo; and a little bit of blur, a vignette here or there, and perhaps removing a bit of drool from the baby's chin are all part of making the kind of "photos" that people want.
Not too long ago, you had do do a little "dodge and burn" to soften the lines and take out the blems. Now you apply a gaussian blur or overlay a coupe of screens, but the effect is literally the same. Warps and straightens are pretty easy, so instead of tilting the negative in the enlarger, you just warp the image, "fix" the leaning building, or to suck in the "love handles" on the "studly model." An over sized nose can be tucked back, frowns pushed into smiles, and such with relative ease. And of course removing that "ugly zit" from the daughters graduation picture is trivial now, but needed the airbrush (or very skilled dodge) not long ago.
One might hope that the news photos will not have been edited in a way to change their meaning, but it so easy to do that all pictures are somewhat suspect. When you add in that the news media seldom "take their own." but rely on submissions from free-lance photographers, news bureaus who buy from free-lancers, (or from congressional "investigators") who have the opportunity to alter stuff before it's seen elsewhere, and who can do so rather easily, "what you see" is NOT necessarily what happened.
"Photographic evidence" is just evidence. To have a "proof" you have to be able to assemble ALL the evidence.