I think you got some good suggestions. Perhaps it is best if you choose one of the following:

1. Refuse to work on wally world bikes.
2. Stock unusual parts/solutions that wally world bikes frequently require.

I can see either choice, but if you choose to work on them the suggestions to be prepared, and keep it simple, are good ones. Just cuz *we* all like to talk about bike stuff with a lot of detail doesn't mean all your customers do.

As for whether to have these folks as customers, only you can decide that. But, from a business perspective I can give an example of where my hairdresser needed a new bike, and since I cycle he asked me to recommend a shop. The shop I recommended doesn't work on wally world bikes, which his bike at the time was, and he didn't want to do business with them because they were rude to him when he attempted to get his bike serviced. So, he and his partner both bought nice new bikes from the LBS that does work on wally world bikes, especially when they politely explained to him how much it would cost to service his old bike vs buying a new better one, and why the new ones were better, etc.