It strikes me as curious that someone who spent a lot of time in the radar industry would make the original statement you made, at least in that fashion. Also, radar is subject to interference as well. In addition, there are many things that act as "natural" corner reflectors that would pose more challenges, I can only think of some mountainous snowy / icey nothern US/Canadian routes and just thinking No way Light sensors and Radar sensors will conquer this.
We need to fundamentally redesign our road systems to accommodate self driving cars. That might happen... in 50-100 years...after we address the already crumbling infrastructure we have. For perfect, sunny conditions, like the roads in Nevada all these self driving startups are doing their testing, with straight flat landscapes, I am sure the tech can work fine. Rest of the country, maybe not so much.