"Livery" implies that the person has some sort of licensed business. I mean, not the word in and of itself, but it's used on license plates in Massachusetts as a designation for legitimate hired car services. At the risk of sounding like Will The Tulip, a person operating an unlicensed cab business is putting him at risk just like a person who picks up hitchhikers is. And no, I'm not going to go so tulipesque as to suggest that this means he deserves to get harmed, but I do think we shouldn't try to pretend as if the person was "just doing his job" when his job is illegal.