What they're talking about I think is the usual statement that self driving cars only need to be slightly better than the status quo (in deaths per mile driven) to make sense because then anyone moving from driving to using a self driving car decreases the number of deaths. From a raw statistics POV this makes sense, if a self driving car is even just a little bit better than the average driver on average anyone switching to an autocar will decrease the number of injuries.

What they're saying (and I agree) is that human nature means people won't be willing to get into a car that's 'just a little better than average.' There's a couple reasons I think that will be true: 1) people generally think they're better than they are at driving 2) moving from people to autopilot moves the responsibility from generic 'bad drivers' causing accidents to a single system. Going from a diffuse responsibility to a more concentrated liability on the part of the manufacturer will probably mean they'll be blamed much more for the failures of their cars.