I do disagree about the mechanism. I don't find that humans are very generous to one another - public opinion very often assumes the worst and takes the least generous interpretation. People are more than happy to vilify a reckless driver who caused a death.
I think the mechanism here is media coverage. We are still seeing articles pushed out by media corporations about this one accident from a year ago. Meanwhile, human drivers kill thousands of people a day and you don't hear a peep about it. So naturally public opinion becomes scared of self driving cars and ignorant of the real issue.
All of that is really tangential to my point, though. My point is that "feelings over facts" is grossly immoral when ignoring facts causes tens of thousands of preventable deaths each year.
The bar is much higher than that. People accept people killed by other humans suddenly becoming ill or briefly not paying attention. We accept human error. We do NOT accept machine error.
So the criterion is that autopilots should avoid a lot of accidents that humans risk getting into (e.g. lack of attention) but it must not be involved in ANY accidents that a human paying attention would get into.
In the end, no one really cares about the overrall safety or the statistics of it all, when it comes to acceptance of new systems. What matters for public perception (so in the end legislation) will be an almost impossible bar for autonomous vehicles, because they don't have the benefit of acceptable human error that we give flesh drivers.