Next time, ask him one of the following two questions. Unless he's a psychopath, at least one will make him rethink his position:
1.) how he'd feel if someone in a car hit him while he was walking in the parking lot because, in the driver's opinion, he didn't get out of the way quickly enough.
2.) if there's so little going on in his life that it would be worth going to prison for running over someone in a grocery store parking lot.
Well, he
is kind of a psychopath.
I've already converted him from the belief that bikes should be restricted to the sidewalk, though... so maybe there's hope?