Why Do People Believe Strange Things?

The way I read it, Prof. Anthony Hall is not guilty of ad hominem. He gives good reasons at least challenging, if not negating, the what and how of Shermer's presentation and exposes its own evasive ad hominem smear tactics of lumping and guilt-by-association:

"Shermer does major violence to the laws of evidence and proof by making vast and unsubstantiated generalizations about so-called conspiracy theorists rather than addressing the diversity of good, bad, or indifferent work done by thousands of investigators exploring scores of circumscribed problems. Shermer’s circus of pseudo-skepticism sets a terrible example for students and junior researchers. They would and should be blocked from advancing up the ladder of professional scholarship if they were to replicate Shermer’s unique brand of materialist evangelization aimed at turning the zeal of his converts against the demonized others. The complex of alleged connections said to link all thinkers with whom Shermer disagrees draws vital intellectual energies away from the tried and true methodology of setting out specific research problems that are narrowly enough defined to be comprehensively addressed with careful reference to relevant academic literature."