Customers are the reason people have job. A single customer is not. The problem is primarily when a customer expresses a gross sense of entitlement due to their status as a customer and they attempt to willfully abuse anyone they see fit. I don't know if it's just typical human arrogance or rampant consumerism, but customer, clerk, or service provider, you're all humans and need to act with dignity and respect. I don't care the cost of the product or the problem with it, it does not entitle a person to be a prick.