The flaw is that the leap from decision in difficult cases to dangerous driving
or other behavior are wild guesses. He sets up straw men versions of what the impact of the evidence should be, then rebuts them.
The reality is that the same psychological state that makes a judge less lenient might also make us better drivers, not worse.
You're missing the point. The point is that the effect sizes in question are large enough that people should notice them in their day to day lives, because the proposed mechanism of action should not only apply to judges, but should apply to everyone everywhere. But we don't see this big obvious affect in other places.
The reality is that the same psychological state that makes a judge less lenient might also make us better drivers, not worse.