This seems to have gone way off the rails. There is no reason necessarily to walk away from a store just because they give poor advice. Some stores have knowledgeable staff, but the vast majority (from what members have said for months) do not. Acquire your fish from stores that seem to have healthy fish, independent rather than chain if possible (the health of the fish does seem to be a real issue between these), but do your own research on issues and ignore advice unless you know personally that the individual has the knowledge.
I was lucky when I got back into the hobby in the 1980's that I had a local store owned and staffed by hobbyists who knew the hobby. After I moved to Vancouver in the early 1990's and got back into fish, I had two similar stores among the then-8 or 9. One provided a terminal so customers could do research right there before acquiring fish. The onus is on the hobbyist/customer to research the facts and make the right decision; it would be preferable to have trained staff everywhere, but this is not common and the situation is unlikely to get any better.
This hobby in my view will cease to exist before the issue of knowledgeable staff gets significantly better. The animal rights folks, who often have a very valid concern, are beginning to turn their attention to aquarium fish. I have previously mentioned a proposed bylaw in one Canadian city that will, if passed, prohibit the sale, acquisition and keeping of all aquarium fish; existing fish will be grandfathered, but as they die off so will the hobby. This is not an isolated case. Sadly, the lack of knowledge among fish store staff, and frankly many hobbyists, only adds fuel to the zeal of these people. The trade in exotic animals has been banned in many places, and fish will likely be caught up before long.