If your on a narrow road where you can't safely pull over, you don't stop. You continue until you could safely pull over enough.

Stopping would cause more harm than good if they're actually trying to get around you.

Sure, I know that, but does a driverless car? All it can see is blue lights right behind it, which could mean "stop right now or we'll shoot you" or "get a move on to the next passing point you can find" depending on context (probably conveyed by the gesticulating of the driver and maybe a loudspeaker).