In short, it's not about the employee at all, but management firmly, totally and unequivocally take the side of and backs up the customer.
An employee can always be replaced but new customer acquisition is five times more time consuming and expensive than existing customer retention. Similarly, poor online reviews due to poor service are the worst form of PR an organisation can get.
I have a cousin who lives in Boston, Massachusetts. Last week he witnessed an incident of poor customer service and a customer complaint at a Wendy's restaurant. The customer called the Manager over and the Manager made the employee apologise to the customer in front of all the other staff and customers.
Then, what often commonly happens in America, is that management get the customer directly involved in the situation, disciplinary process and often let them decide on the sanction. The Manager therefore asked the customer what they would like to happen to the employee concerned as it's their call, and the customer told the Restaurant Manager that they want the employee fired to act as an example to the others.
Management agreed and told the employee in front of everyone that: "I am afraid that I am going to have to let you go, so collect your cards at the end of the shift as you are terminated."
In America, you can legally do that as everyone is on 'employed at will contracts' and they do not have a system of employment tribunals or labour courts in the same way as in the UK or EU. The law generally backs and takes the side of business over workers, and trade unions have traditionally always had far less clout, power and influence there.
However, is that such a bad approach and system as that have always had lower levels of unemployment on their side of the Atlantic and are the largest advanced and industrialised economy in the G8 grouping?
Hire and fire in other words. You don't get job security in the US and they can put you out at anytime, unless its not due to a protected characteristic.