I don't think a armonster was quite claiming it to be "obviously correct". But rather taking it for granted that this a valid hypothesis:

- We would have gotten most of the social utility of automobiles, without most of the social negatives, if personal vehicles had mostly never happened.

And implied from that, we should stop having them now.

Given the known ills of society, I think those negatives are pretty uncontroversial. To the point that personal car proponents have some burden to explain why we should keep it up.