GGP talked about autopilot acceptance

GP is talking about holding Tesla responsible the same way we do with drivers ala insurance and regulation

Parent says to only hold driver responsible

So while the parent did not mention autopilot per se, the comment can only be interpreted in the context of talking about autopilot/ like systems. Otherwise, "Always prosecute the driver." does not make sense. That is the only option when you are talking about standard accident investigations(baring manufacturer defects e.g. faulty ignition switch, rollover/tires, sticky/abnormal acceleration pedals), nothing else in a standard car has ahem autonomy.