There are very few cases in which journalistic cropping lies, simply because journalistic photos always focus on some central issue. That's why the photographer is there. If you crop out the central issue, nobody wants the photo. (If Andrew is referring to the same "famous photo" that I'm thinking of, t hat was not a simple crop; two photos were cropped and then stitched to make an entirely different scene. The LA Times photographer was fired.)
There are cases, most often seen on TV, where cropping eliminates an issue, but not an obvious one, and those crops do create a lie. Where you see this most often is when there is a public demonstration against something, but only a few demonstrators show up. The TV crew then crops in close, eliminating empty space, with the demonstrators crowded together, so that it's impossible for the casual viewer to tell that the "demonstration" only attracted twelve people in a city of three million. A journalist, however, may look at the marching crowd and if you see the same face three times in 45 seconds, you'll know what is going on.)
I completely reject Tony jay's position here, simply (imo) because it's the kind of naive college-dorm argument which asks, What is "reality?" What is "objectivity?" Photography is quite a pragmatic pursuit, and at its bottom level -- the unattended video camera which simply shoots everything that passes within range, with no post-manipulation or deliberate cropping -- can provide quite objective evidence, good enough for judges and juries to use in sentencing a person to death or long prison terms, as we're seeing in the Boston Marathon trial. In that case, almost all the evidence, and even the pursuit and arrest of the guilty people (and the killing of one of them) was conditioned by photography. I would argue that that is photography at its most fundamental level. There are many manipulations possible after that, done for all kinds of reasons, and some of them subtract from the objectivity of the unattended camera, and some of them may incrementally add to the reality. I think such things as HDR, used with care, may enhance the the reality of a photo; and, compared to the basic unattended camera standard, so might a different selection of ISO, shutter speed, aperture and so on.
The decision between what you'd argue is reality and what you'd say is unwarranted manipulation -- the line, if you want to use that word -- has little to do with the photograph, but more to do with honesty. As I wrote earlier in this discussion, I have no problem with anything done to a photographic file, as long as the manipulation is disclosed if there is a possibility that it might be mistaken for an unmanipulated file. The standard "It sells better" is not, in my opinion, an excuse for lying about the condition of the photo.