In all fairness, the author is probably right that his or her clients would change vets if they told the client to stop owning brachycephalic dogs, and the client would be right to do so. People are deeply emotionally attached to their pets; it'd be a bit like a doctor setting a kid's arm telling the parent "These extra-long arms are prone to breakage; you should consider having children with someone with the genes f…
People are deeply attached to their pets, once those are actually born and part of the family.
Here the vets just need to stop working with breeders. Those are not emotionally attached to their pets, and they are the one considering making specific adults mate for some specific genetic material.
Stopping this market has nothing to do with telling some family that they should just give up on their dog. It's far sooner than that, before the animal is even born, that a change has to be made.