Rather than quitting, he should have continued being a vet so that there would be 'one more honest vet' in the neighborhood. While i'm sure some vets put making money before animal welfare, that's not always the cost. Pet insurance is necessary for long term diseases which require medication for the rest of the pet's life. If your dog needs eye drops twice a day for the next 6 years, it can cost a fortune, but with insurance you dont have to euthanase him just because you cant afford his treatment.
Humans are willing to go through 'barbaric' treatments for half a year extra life, so why wouldn't animals? It's a controversial matter, but I think killing an animal to save him the pain is just as unfair as forcing him to go through with the treatment.
I can't help but wonder weather he was just submitting the article for attention or publicity. Either that or he has the completely wrong idea about vets.