At the risk of rubbing everyone on this thread the wrong way, the responses I see from many of the LFS employees are:
1) Unprofessional
2) Not actually looking to address the ignorance issue
3) Arrogant
4) A poor way to run a business
There's a post early in this thread about a comment someone made to a guy regarding his wife giving him crabs. Quite frankly, if I had been that customer, I would have come across the counter, assault charge be damned. While it was meant as a joke (albeit a funny one too), some guy working the counter at a LFS lacks a great deal of familiarity with me to make such on-the-edge jokes such as those.
Instead of offerring a rolling of the eyes, a snide remark, a sigh, or any of the other petulant responses I see here to an ignorant customer, try actually educating them. As an advocate for this hobby, and someone in the customer service business, that is something you SHOULD be eager to do. Furthermore, such education is known to be one of THE best techniques to securing extremely loyal customers. If you tell them to go somewhere else, and they do . . . what does that solve? Now they simply go somewhere else to kill fish. Is the breadth of your concern for this hobby limited only to the fish in YOUR shop?