In my totally arrogant opinion, there is no lower form of life on earth than individuals who are rude to waiters, or cab drivers, or store clerks, or telephone tech support people.
"But isn't that hypocritical, Niccolo? You're rude to people all the time."
Why, thank you. Yes, I am. Breathtakingly rude.
I am not, however, rude to people who are in a position of "being nice to me, no matter how wrong I am". The people I slag are perfectly free to be rude right back. They don't have to worry about winding up in the homeless shelter because an arrogant prick (such as myself) whined to their spineless boss. You'll NEVER see me being rude to a customer service person. Ever.
People who are rude to clerks and waiters are sociopaths, pure and simple. They view others as instruments of their own pleasure, not as human beings with rights and feelings.
If I'm meeting with a potential client or employer, I pay careful attention to how that person treats service personnel. If he's a jerk, a GIGANTIC red flag starts waving in my head. I generally decide that I don't want to have any kind of business relationship with him; the few times I've violated this rule, I've regretted it later. You see, the way your potential employer or client treats the waiter is the way he's going to treat YOU, given a chance.
Oh, yeah, the "customer" is always right. What about the OTHER customers? You know, the ones who wind up paying more money because Joe Asswipe held his breath until he got a free replacement for the unit he broke? Or the customers who pay more for their dinner because Joe sent his steak back five times, like a picky two year old? Or the customers who are WAITING ON HOLD while you're walking Joe through the instructions that are on page one of the goddamned manual? Or the customers who get a trainee every time they call because Joe's constant torrent of abuse has caused anyone who has a shred of self-respect to quit? What about them, huh? Platitudes from a 1910 management handbook aren't going to do much to help them out, now, are they?
If you're in management, you need to realize that "customers" like Joe are a net loss. If you're worried about "word of mouth", you need to realize that Joe is going to bad-mouth you anyway, no matter what you do. Chances are that Joe's friends (if he has any) and business associates know perfectly well to discount 90% of the crap that comes out of Joe's festering pie-hole.
If you're extremely lucky, Joe will start dealing with your competitor and eat into his bottom line for a while.