Now, I'm all for adopting from a shelter (all of my dogs/cats are rescues), and I'm also very much against the bad breeders that give all breeders a bad name. BUT...I do believe that there is such a thing as a good breeder, even though some animals are being PTS in shelters. This breeder must be pretty good (maybe not perfect, but I can't say for sure because I have no info on the breeder), because he/she took the dog back when the original family returned him. If all breeders did that, there would be no purebreds in shelters EVER. Not for long anyway---only until the breeder found out one of her dogs was there, and came and bailed him out.
Dogs in shelters are not a by-product of responsible breeders. Mixed-breeds are at the shelter because someone was irresponsible with their pet. Purebreds are at the shelter because the owners weren't responsible, AND because the breeder was not responsible enough to take the dog back if the owners couldn't keep it. Responsible breeders do not add to overpopulation or have any impact on shelter populations. Most responsible breeders also are involved in rescue, and help in that regard as well.
First of all, if there was no breeding at all, there would be no purebreds at all. With cats, this wouldn't bother me. I have no particular preference when it comes to cats, I just like plain old moggies. It wouldn't bother me at all if all purebred cat breeders went out of business. But of course some people really like purebred cats, as is their right (if the cats are bred responsibly). However, purebred dogs are bred for different purposes. I can't use any old mutt to herd my sheep----I need a Border Collie! So I definitely think that preserving the purebreeds in dogs is important. And there is so much variation in dog breeds that, if you have your heart set on a PWD, you aren't going to want a Lab. And there just aren't any PWDs in shelters, although some are in private rescues.
Second, there really isn't much of an overpopulation problem with dogs. Most dogs in shelters are there because their families didn't care enough to train them properly, not because of overpopulation. There were about 4-5 million pets PTS in shelters last year, but only about 1 million of them were dogs. It's still too many, but the euthanization numbers will never be zero, because some dogs are mentally ill; so badly aggressive/neurotic they cannot be adopted to anybody. And other dogs are old or terminally ill, and are dropped off by their owners to be PTS because the owners can't afford to have a vet do it. So there will always be some pets euthanized in shelters, even if every adoptable pet was adopted. Cats are seriously overpopulated in most areas of the U.S., but it's an entirely different issue with dogs. Some BREEDS are overpopulated (around here it's Labs, other places hounds, other places pitties), but most are not.
Third, I think a family needs to find the right dog for them. I would much rather have my grandma (for instance) buy a purebred Toy Poodle from a breeder (even a BYB) than adopt a large Lab/pittie mix from a shelter. She just wouldn't be able to handle it, and the situation would not end well for either of them. A dog needs to be a good match for his owners. A dog who isn't well matched to his owners is far more likely to end up in a shelter. A dog that IS well-matched to his family will likely have a long and happy life with them.
---cats is cats, but dogs are entirely different. I do not fault anyone for getting a purebred dog, IF they buy from a GOOD breeder. Good breeders need all the encouragement they can get, because things are getting very rough for them. The current laws encourage inhumane mass-producing puppymills and discourage humane, small-scale hobby breeders. So it's rough enough trying to find a humanely-bred dog, nobody should be criticized for doing so, especially after they've done all their research.