Well, the OP talked about not cropping for artistic reasons, because it "lends authenticity to the scene".
Yes, but Chris said that the "authenticity" idea came from Cartier-Bresson. It didn't. If anyone doubts that I'd suggest he read The Mind's Eye.
It's a very short book and an easy read, and has most of HCB's photographic philosophy carried over from Images à la sauvette,
also known as The Decisive Moment.
I agree there is always image degradation when cropping, but with good glass and high resolution sensors you can take a hit without it being noticable in the end-product (except for pixel peepers, but we're talking about art here.... ). I look at it much different now than the times I shot color slides on film, where the framing needed to be near perfect (and suited to the aspect ratio of the camera) to avoid all kind of different sizes in a slide show.
I agree with you, Pieter, especially about the fact that current technology makes image degradation a less serious problem than it was when Rob was active as a pro. But that wasn't what HCB was talking about. If anyone wants to go back through the thread, he'll find plenty of discussion about the real issue from HCB's point of view: visual integrity.
I like your example of shooting color transparencies. I suspect everyone on here, except possibly the youngest, has shot them. Okay, folks, when you shot color transparencies (slides) did you shoot with the idea of cropping? I doubt it, because unless you were very unusual, with very unusual equipment you couldn't
crop. So what did you do? You were very careful to get the composition and lighting correct before you tripped the shutter.
Look, nobody on here is saying you must not crop!
What the sensible voices are saying is this: It's worthwhile trying to get the picture right in the viewfinder before you trip the shutter. That's when you have options that'll never be open to you during post-processing. In other words, shooting loose and hoping to find a picture later not only is sloppy work, it's lazy work and a sign that you're not quite sure what you want to do -- a deadly state of mind for a photographer.
Cartier-Bresson would tell you that you never should crop, yet we know that in two of his greatest pictures he cropped. I posted an example about two-thirds of the way down page 2 of a picture I shot a few days ago where I knew I didn't have time to move closer before I made the shot and knew I'd have to crop. Had I been HCB I'd have tried to move closer so I wouldn't have to crop, and I'd have lost the picture. There are always situations like that. But that's not the same thing as banging away and hoping you can find a picture in your files later on.