"No idea how we'd do that" is a good way to condense it. But it just seems like every promising foray into improvisation done by computers ultimately turns out to be a fata morgana or a false positive. What hopes I had before this week have been put to bed now. Put differently, how long must we search (and how many billions do we/Google/rich people spend) before we ask ourselves the hard question whether this is doable at all. That may very well turn out to be a failure of imagination on my part, but personally I feel like the position of "this is, for the forseeable future, iron law" is preferential to "it might work some day (we just don't know how, and have no practically attainable idea of how)".
I have seen four, possibly five forays into artificial intelligence in my lifetime. None of them have panned out in a "three laws of robotics" / cogito, ergo sum sort of way but by sheer process of reduction, we keep getting closer to an answer. That answer might be "never." Researchers keep swinging at the ball, though, which leads me to believe they think there's an outside chance they'll hit it out of the park. By way of contrast, in college I sat through a two hour lecture from a couple guys who had modified collective pitch helicopters with broadcast transmitters, gyros and servos to put a stereoscopic VHS-grade turret on an aerial platform. Their build cost was around $20k, their bird was an easy 50 lbs of nitromethane-powered terror and it required a tremendous amount of skill between two operators to manipulate. I had Costco pizza for lunch? And they've got FPV drones for $50 that will fit in your shirt pocket. There are some problems that can be brute-forced through existing technology and some problems that can't. My personal sense of the state of self-driving cars is that our technology will totally drive a garbage truck without much drama but getting you to work via the freeway is never going to be safe enough. Is it a leverage problem or a breakthrough problem? I don't know enough to have an opinion... but I know enough that I think GM is being pretty shady about it.