First, the AI hype train. People think that calling something "Artificial Intelligence" implies that it is artificial, yes, but also, critically, that it is intelligent. Many enthusiastic people, and also many policymakers, don't fully realize the extent to which machine learning is constrained by both the quality and nature of its training data, and the capabilities of the larger, non-intelligent, software framework that it's being plugged into.
Second, that we have one case study - the post-mortem analysis of the fatal pedestrian collision in Arizona - that strongly indicates that commercial products are not free of the sorts problems being highlighted here, and that, unlike what others have suggested, misclassification problems aren't necessarily an issue that's isolated to individual frames and that will come out in the wash when the software is dealing with a stream of frames.
Me, I think that self-driving cars are probably a lot like nuclear power. In theory, yes, it is a great idea. In practice, there are a lot of little details that one must get right, and there seem to be a whole lot of opportunities for flaky engineering decisions and incompetent public policy, both enabled by insufficiently-tempered optimism, to scuttle the whole thing.