Like many others have said, right or wrong, the customer is always "king" (or queen).
That said, though... doesn't mean he/she is not a complete arse!
Having been in "customer oriented" fields (sat TV tech) where part of my job description was to practically kill myself for the customer, it always kills me when you hear people say "customer service is dead".
Yet it's usually those same people that are the rude, whiny, and selfish (can't use the select adjectives I'd like to here, lol) types who demand something way above and beyond what the service person is supposed to do.
You may be paying "good money" for whatever service, but odds are, little if any of it is going to that particular employee you feel the need to lambast. Always makes me wonder why they feel doing everything in their power to make that person miserable is going to inspire them to provide anything more than the bare minimum necessary to stay out of trouble.
Seems it would do everyone, on both sides, a lot of good to remember, courtesy is a two way street.