Dissatisfied customers, angry clients and anyone else who demands that an employee be fired should be immediately terminated from their own employment on the grounds of petty stupidity and a failure to understand how a job loss can impact a family.
One bad experience or one poor decision does not justify the demand for the possible financial ruin of an individual.
Customers complain and receive refunds and compensation if the complaint is valid and the business is reputable. Employers terminate employees when necessary. This is how the world works.
To demand the termination of an employee demonstrates a penchant for self-righteous stupidity, which is the worst kind in my humble opinion.