I don't think that's mutually exclusive with Waymo working on their electric autonomous vehicles, nor that halting Waymo's testing would lead to greater access to public transport. Safer cleaner roads should hopefully even benefit busses, coaches, trams (and bikes) that have to share the road with cars - and the same self-driving technology can likely be adapted for use on public transport vehicles.

China, for instance, has extensive public transport in addition to a fast-growing autonomous vehicle sector. As useful and underutilized as trains are, there will likely still always be a non-negligible portion of transportation that road vehicles are just better suited for, which should be made as safe as possible.

There is also that it seems unfortunately difficult to get financial/political momentum behind building public transport in the US, whereas Waymo's services are something that's already happening and GP is implying should be stopped - which I feel flips the "Why not just" in terms of which is the course of least resistance (but, to be clear, we should definitely still be pushing for public transport).