I figure it's important to understand that people who work in bike shops don't make very much money. I should know.

That said, any bike shop worker that defaults to a mean attitude or nastiness works at a bike shop that is not worth frequenting.

And that said, many customers are often bigger 'holes than they think they are. I am never mean to a new customer, or to a repeat customer who is not nice but is not straight mean. However, anyone who comes to me for help and...

-insists upon special discounts,
-insults my knowledge on the subject of bicycles,
-suggests that I am trying to work him/her for cash, or,
-is nasty...

...no longer deserves politesse, amicable treatment, or my profound and extra-mile interest in his or her bicycling ills, and receives none. My (the worker's) obligation has then ceased to be personal, and has become purely professional, which seems to bother some people. An employee who is mean right off deserves no business. An employee who treats his customers following the way they treat him is human and sane. An employee who treats all customers the way they think they should be treated, all the time, regardless, is a robot.