The whole thing gets interesting when you look at the judicial side of it: Who is responsible in the case of an accident? The car manufacturer (if it was a software failure)? Then even one accident triggered by it is too much.
The idea that 'even one accident is too many' is a joke when you consider how many accidents there are with human drivers, and yet we accept them willingly. If there are 30,000 deaths per year from human driven accidents, then surely the real answer to how many accidents by computer driven cars is acceptable should have an upper bound of 29,999, right? Why isn't it acceptable if it saves even one human life, rather than being unacceptable if it costs one?
Unfortunately, we as a group don't tend to be very logical, and love to spread blame, so I am afraid we'll take a long time to start saving lives. The data on the self-driven cars on the road is pretty overwhelming that they are safer than human drivers, but unfortunately there will be those (as in this thread) who believe that is true of everyone but themselves.
Its going to be a long road to acceptance.