The silence that followed was worth more than gold

Depends on what the customer is "interrupting". I had a teller having a personal phone call and I asked her to please check out my purchases and she had the nerve to tell me I was rude. If she had been helping another customer then I was the jerk. But she was talking to a friend.

Depending on what store you work at, customers always come first. That customer has every right to complain about you to the manager.