"First, don't lie" that should be the documentary/new photographers rule of life. No manipulation, cropping or coloration whether done in camera or not, should provide significant distortions of what actually happened. Unless of course the caption reads..not captured, ten U.s. soldiers where slaughtered 2 minutes beforehand to place some crazy US soldier in context.
Same in any documentation. That's the ethics of it.
For portraits, glamour, art the sky's the limit. There are no valid barriers to method or extent of image alteration.
For pictures accompanying sales/advertising/political campaigns of, the moral issue raises it's head once more.
That however, we are used to.
Pictures in the news, however are too important to be twisted to represent a personal "view" of the world. We should expect and demand that documentation represents what our own eyes would have readily seen and not a view shaped by propaganda.
I for one believe that in art, distortion, editing cropping and so forth, give the compelling meaning to otherwise less emotionally significant imagery.
It is unimportant as to whether this mpact is achieved by a T/S lens, panning a still shot, altering in P.S. or burning part of the picture over a candle flame.
As art, it either works, or it doesn't.
Mark Tucker's art works strongly for many of us. I'm impressed what beauty he achieves by mechanical means. Still, it's the effect he achieves, not the methodology that is of any significence.