it is an apples-to-oranges comparison because AP is only used on highways where traffic incidents are already far less common per mile driven.
True, and that kind of flawed argument bugs me. However, there is also data that showed that accident rates went down significantly on the same cars after Tesla first enabled autopilot via a software update. This is much more compelling to me; if the same people driving the same cars in the same areas became less likely to get into an accident as soon as autopilot became available, then I don't see how you can really argue that the feature is not beneficial to safety.