Thanks for the reply. I'm not arguing that scooters are beyond reproach. I'm for development of scooter regulation in a way such that we as a society can harness the benefits from it. Being against them just because they don't work in the current regulatory + road system setup in my mind is at risk of forgoing potential massive benefits for us as a society.
I don't think we should be using the argument of 'well, the externalities for cars are worse' when deciding how to deal with the externalities of scooters, though. By that argument, we only have to ever make sure our externalities are better than the very worst offender in order to be beyond reproach.