Sometimes retouching or "doctoring" a photo has real aesthetic necessity - to remove blemishes in the photo or unfortunate objects such as a tree seemingly protruding from someone's head or a signpost blocking part of the exterior of a home. Sometimes on a particularly gloomy, overcast day, we want to brighten the mood with a lighter sky.
Aside from little cosmetic helps that we can do in retouching photos - and we used to do this in the darkroom anyway so it's not a new concept at all - we need to be careful both from a spectator standpoint (viewing the photos) and in showing such photos to our clients that we are not mistaken in what we see or perceive.
As we establish a level of trust with our clients, they need to be able to believe what we are telling and showing them and that we have their interests in mind when we create a plan to help them. We must never do anything to violate this trust.