At least the dog was a SPAYED dog. Whatever reasons they have to re-home the dog is THEIR reason. If you read the Craig's List ad, I think they cared for their dog. She was/is spayed, had been obedience trained and vetted.
How many dogs/cats are re-homed without being spayed? Without being vet checked? Without being trained? It sounds like this family put a lot into this dog, and to have someone "slamming" them on a pubic forum like this without giving the people an opportunity to respond is silly.
Would it have been better for this family to just turn the dog loose? To take her and abandon her on someone's "farm"? Then we would have the posts that someone abandoned their german shepherd, it killed my chickens, so I killed it. What is wrong with re-homing a pet? Sometimes things don't work out, and again, at least they are responsible pet owners because the dog is spayed so she will not be contributing to the puppy population. What about the "breeders" that breed without any concern for the betterment of the breed but post their cute puppy pictures here? What about the support they receive? How many "breeders" utilize this website alone as a method of advertising their puppies for sale? What does that make them? To me, it makes them a bit worse then a family that is looking to re-home a SPAYED dog because of circumstances such as moving.