Been there, but didn't do that. When I first moved back to Daytona before finally retiring, I worked for a while at a local camera store. Nikon was good about paying incentives for selling their product. Canon less so. But, as a long-time Canon user with a large investment in lenses, I didn't plan to switch.
As far as customers were concerned, I tried to sell what they could use. First question was always, "what have you got now?" I never tried to convince someone to switch from one brand to another. The choices were even greater for point and shoots and the boss would always try to sell the latest and most complicated to everyone that walked in, often elderly people who only wanted to be able to snap a simple picture. He got a lot of returns, but it was his business. I sold them the simplest camera that would meet their needs and got very few returns.
On the other hand, an employee at another local store that has since gone out of business due to the economy, was the complete Film and German camera snob. One of his tasks was to assess trade-in and consignments and determine their resale value. When I bought a new lens and put an older lens up for sale, he would constantly run down anything Canon and compare it negatively to Leica or Contax.
I had found a nice deal on a 24-70L while vacationing in St. Thomas and was putting my older warhorse 28-70L on consignment, when he started telling me what a piece of S**t it was. This was the zoom that had shown a lot of news photographers, including me when I first purchased it, that you could match results against a prime lens. It was too much for me and I unloaded on him. I won't try to detail the rant, but I berated him pretty thoroughly. Enough that his boss came out and took over. Later, she said she had to give him her own lecture since 20 to 25 percent of the sale of any item on consignment went to the store and his running down Canon was not in the best interest of the shop since Canon was their main supplier.
Thing was, the guy was a decent photographer. He did do good film work and he was probably right about the comparative quality of stuff they didn't offer for sale. In fact when they had some nice used glass for sale, Contax G or Nikon lenses, it often was one of my consignments as I converted to digital and experimented with adapting other lenses to the Canon EOS mount. So, in the end, I regretted my loss of temper. His real mistake was merely calling one of my proven quality lenses a piece of...