"If people come in asking for a room, and you think they look like trouble—rowdy college students, say—if you have ‘Vacancy’ out there, you’re kind of obligated

"If people come in asking for a room, and you think they look like trouble—rowdy college students, say—if you have ‘Vacancy’ out there, you’re kind of obligated to give them a room,” to put it another way, the "no vacancy" sign makes it more difficult to discriminate