All generalizations are meaningless.
What’s more, they breed false beliefs that can do harm. They’re so attractive in their simplicity, and that’s why they take root.
So it is with the claim “The customer is always right”. You can use it in an ad (though it won’t do much good there either), but as a guide for everyday work? Spare me!
I think it would be better to replace it with something like “My customer is my friend”. Look: friends aren’t always right, but people don’t stop being friends because of it. You help friends, you talk to them, you support them and make them happy, and friends return the favor.
That’s my little business philosophy.