Customer may be a king as the company serves him, but he is certainly not a king in the meaning that he can do what he please, including insulting the service provider.

You need two for the tango, and the same way the provider wants your money, you want his services. It’s a fair exchange of money for services, and both parties are on the same level. Just because you are on the money side on the barter doesn’t give yiu any extra privileges.

Example of the dwalters is a valid one – just because you are paying money for food doesn’t give you the right to insult the waitress, or even the restaurant owner. Do that and you will be asked out, and chances are never served again.