Evan Nailed it I think. And you may take this to all walks of life(work, romance, financial, etc...). As a consultant, this is an every day occurance. You learn to let it roll off your back. It is even fun to grin when they come back with a tail of woe. I don't bother with "I told you so's".
The difference is, with your examples, the life (or quality of life) of an animal and/or it's loving family is at stake.
Everyone is a dog trainer and even some hang out their pro shingles with minimal experience. I have the same thing even with family members, ask questions, then do whatever they want to do. An old saying, you are a moron in your own town and 20 minutes away you are a expert. Human nature I guess.
The ones that annoy me the most are the ones who ask a question, you take the time to then them and answer and the next thing you know they are asking another person the exact same thing. I have no patience with them and the next time they ask my reply is I don't know ask so and so.
I think that that many do not think that they need to be so particular BECAUSE they only want a PET. After all you and people like you need something different than just the pet.
Too bad they don't understand that our "performance" dogs are also pets. Too bad they don't understand that encouraging poor breeding practices, often times produces animals who suffer from poor structure, are miserable with allergies, and other problems.
I can think of a couple folks who generalize about their whole pack of dogs. (My dogs won't pick up ABTs/Dokkens. My dogs don't like to (XYZ)"
This happens in so many aspects of life, and it seems to be highly correlated with how much something costs, or how hard you have to work to attain it. There is nothing cheap or easy about quality. That's why it's so valuable.