Moire L. answered 07/31/19
Adult English, Reading, Writing, ESOL, and 2025 Citizenship prep
What a great image.
It means that the bartender is so charming that he can make an owner surrender something that the owner would rather keep.
I've never heard that particular analogy before, but similar ones are "He could sell ice boxes to Eskimos" or "He could sell sand to an Arab". Less racist comparisons include "He can charm the birds out of the trees".