I know a very reputable Aussie breeder from my training club who sometimes breeds Homozygous merles(Merle to merle.), to get amazing coat colors. Nice lady, she wins in the ring too. Her dogs are fantastic. This year Westminster awarded Aussie BOB to a dog who's stud was a blind, deaf double merle. Westminster Rewards Cruelty
I don't think it's a good thing to do, but a lot of breeder's, back yard, and top of the food chain, well respected CH CH CH winners, breed for select traits that are frequently not good for the health of the breed. Short noses, unnaturally angled bodies, freakishly large heads, traits that would never occur in nature. I have friends in the conformation world. Breed clubs decide what is okay, and you can follow the rules, or get out of the ring.