I think manipulating images, by removing elements and adding in stuff, is comparable to doping in sports. By artificial means you make yourself better than you are, at the cost of your competitors and audience. It's not okay. I just can't have a "who cares?" attitude to that. I love photography, and I don't want it ruined by photoshop manipulation.
It's genre-dependent though. If you make a work of art, it's different from documentary work and it can surely be a composite. As a rule of thumb I think one can say if it's obvious the image has been manipulated it's okay to show it without comment, otherwise it should be presented together with a comment.
These types of discussions usually unfolds into something "but is grading okay then, increasing contrast, changing color balance? If that's okay than surely anything must be okay?". And of course the relation between photoshopping and an arranged scene, is an arranged scene any better or not? There are numerous examples of claimed "wildlife" photographs that was actually shot in a zoo. That's not okay either.
It's impossible to draw a strict border though, as it's about context. What's perfectly okay in one context may not be okay in another.
As McCurry is known for documentary work, I find his photoshopping business very disappointing. I know too little to say if it's a scandal or not. If photoshopped images has been in say national geographic and broken their authenticity rules, then I'd say it's a scandal. If it's just about his prints in galleries without claimed authenticity it's less so.
We had a scandal in Sweden five years ago when a well-regarded award-winning wildlife photographer was caught with gross manipulation of images, adding in animals, sometimes not even using his own raw material. His explanation was that he couldn't handle the pressure to deliver top notch images that the audience was expecting from him so he started editing first a little, then a bit more, and a bit more, until it was totally out of control. The manipulations I've seen from McCurry are far from being that bad but I guess the reason behind it could be the same, he no longer feels he can deliver the same quality which made him famous without cheating.
