I think the OP was referring to the advice many people give, which is to insist the LFS feed the fish in front of you to watch for a good feeding response, compared to teh reality that in some areas, "quality, sought out fish" go very quickly...
I would not shop at an LFS where I got pushback on asking them to throw a little food in the water to watch the feeding response!
Feeding the fish every time someone wants to see it eat can be problematic as well.
For example, we feed our fish before we open. This takes about 30 minutes as we make sure to not over feed by carefully adding food to each tank and watching how each fish is eating.
You are not the only person who wants to see the fish eat and obviously feeding a tank 10 to 15 times a day isnt feasible.
Before I opened my store, I purchased a Crosshatch Triggerfish from an lfs who dropped in silversides when i was looking at them so that i could see them eat. He ate like a pig and I said bag'em up. He put the fish in a bag and placed it in a foam cooler.
I got home 20 minutes later. Opened the cooler when I got i side and the trigger was dead and there was probably the equivalent 5 silversides in the bag.
Called the lfs and he said there was nothing they could do a out it. $1200 and a beautiful fish wasted due to the fact the fish was over fed and stress of bagging him made him puke up all of the food and poison himself.
Most likely if you get what you call pushback its due to responsible people thinking of the wellbeing if the fish first.
If you want to see the fish eat then ask the store owner when he feeds hos fish and make sure to be there to see it eat. Im sure they would not have a problem with it.
Just letting you guys here some different perspective on this issue.
I wont sell fish that i know won't eat because I dont want to set my customers up for failure.
I want return or long term customers.