> The onus is on the people presenting the result, in all cases. That's the scientific process. The authors need to defend the null hypothesis as vigorously as you can.

The authors posit plausible evidence (observed variance across states with different introduction dates of laws, car ownership, going from 2 to 3 children) that car seat laws was a deterrent to having more than 2 children. A substantial criticism would be to come up with some possible confounders or alternative model of the variation. Saying that it might be caused by anything is a low effort dismissal.

> Have you ever gone through a peer review process? Seriously?

Yes I have, on both sides. Maybe it differs by field, but I (and my fellow PhD students) took it serious enough that we rarely read and finished writing a peer review within a single day. (This was mostly on economic theory / methodology papers, where even understanding the paper can take multiple days.)