This is so appalling. What really irks me is there seem to be so many people who do this sort of thing. I once met a man with a really cute little dog who he'd rescued--his was an adult animal, rather than pups like yours, but it was the same sort of story except in that case the dog had clearly been abused--and he said "You wouldn't believe anyone would do that to a dog, would you?" and I was forced to say "Unfortunately, I can believe it, because I've heard too many similar stories."
Good on you, Gin. At least your puppies' story will have a happy ending. Obviously, you can't keep them all--or perhaps not even any--but at least they have some hope of finding someone who will appreciate them. Such cuties!