I'd never disagree with anything Ansel Adams has to say, but I'll point out that photography can be documentary in nature, and people get disturbed when you cross some kind of nebulous line. One classic example was the magazine that darkened O.J. Simpson's skin in his mugshot. Another example was a Newsweek cover where they superimposed barcodes on some fighter jets as something of an illustration to go alongside an arms industry piece.

In the modern world, fashion photos are significantly manipulated. For some "singles dating web photos" that I did for a friend of mine, I removed some acne from his lip, and otherwise just did the usual brightness/contrast/saturation/color balance tweakage. Is that manipulation, or is it just making the photo look more like he's supposed to look? Hard to say. What if I'd whitened his teeth and emphasized his blue eyes? Where is the line?

The line, I suppose, is about intent. Ansel wasn't trying to convey a scientific fact about the amount of moonlight cast on a particular night. This contrasts with many scientific publications, which mandate that authors explicitly document any and all photo manipulations they perform. For the dating web site, the intent is to market yourself, which clearly allows for some bending of the rules, so long as it's clearly still the same person, but I'm sure even that's too fuzzy.