being a vet has nothing at all to do with fish. You cant get mad and not go to the vet thinking they must know better. It is not their responsibility to know about fish.
As a veterinary technician (or "animal nurse" of the term doesn' say enough), I feel the need to comment on that. First off, a vet should know better than to buy an animal without doing research on it; what kind of message are you giving your clients by having animals in such poor conditions? It is immensely hypocritical to preach proper animal care and not exersize it yourself. If I was a fish knowledgeable person, and he told me something about how to care about say, my mouse, I'd double check what he said because his lack of knowledge on that subject would make me insecure of him as a vet in general. Maybe he's a perfectly wonderful vet, but what I'm trying to say is that he is giving a negative image to his clientel. The fact that they are "just fish" doesn't mean you don't need to do your reading before getting one.
Furthermore, don't assume that vets never hear a peep on fish care in all of their years of schooling. There was a whole CHAPTER in my animal husbandry and nutrition text book devoted just to fish (there was even a section on madagascar hissing cockroaches). There are even aquarian vets. So chances are, he/she probably was exposed to at least some fish care knowledge while in school. And besides, even if he doesn't know squat about fish, as a vet, he should have some concept of the humane care of animals. I don't know about you, but I don't see two gallons as being especially pleasant for any fish, let alone several. Most educated people really frown upon the fish-in-vase setup because they realize that retailers lie to sell more, at the cost of the fish dying, be it bettas from improper diet (plant roots for a carnivore... joy), goldfish from too much ammonia, guppies from cold water, etc.
So, as a role model for the proper care of animals, it is very poor on the vet's part to have such a setup in his office. He probably wouldn't listen if someone brought it up as a lot of vets have an ego about how much they know even when they're clueless, but it might be worth mentioning anyways. Either way, poor fish!