You're right, but he didn't lead with that info. Cops are nervous scared boys, they want to control all angles of a situation, something that can never be done, but the logic holds. If he had assured them, hey, I know you're doing your job, I'll be safe, not interfere but I'm giving my son a ride. What's the safe distance you'd be comfortable with? None of that would have happened.
Of course, we could say the same if they had just been civil and human, but that isn't very likely.