Some people are jerks, and for some reason need to loudly proclaim to the world that they are jerks. The counter lady obviously recognized that.
By the way, what the counter lady did here was a classic way to intervene in harassment. Engage the target in conversation, cutting the harasser out. They get to stand there on the side, making noise and pointedly being ignored, which really does make them look foolish. If they are persistent, inviting the target to walk to another area can help, that is "Say, we have this product on the other side of the counter area you might like", or "Hey, lets grab a cup of tea and chat."