His mental model of the issue is just plain wrong. I think he might be dumb? The bit he seems to fail so hard on…
if his kids are vaccinated in this hypothetical scenario with the hypothetical super safe, super effective vaccine… then QED… he believes they are perfectly safe, no?
If the vaccine works as he described, then his kids can safely inhale the airborne virus and be fine. The prevalence of the virus is irrelevant… the prevalence of sick infectious people is irrelevant… unless of course, the vaccine doesn’t actually work.
His position is paradoxical. It’s just wrong.