They were jokingly talking about Bill basically portraying 'Michael Schumer' in ATC. Which is someone Dan dislikes. Probably a sceptic in real life.
This looks like a job for... CAPTAIN PEDANTIC
Yup. Skeptic with a capital "S", founder of the Skeptic's Society, editor in chief of Skeptic magazine (which has been problematic for a few years now), and author of several books. Got two of his books on my shelf; Why People Believe Weird Things, and The Science of Good and Evil.
In 2013, PZ Myers posted an allegation from an unnamed woman stating she had been raped by Shermer, and later another woman came forward stating he tried slipping a pill into her drink.
So... complicated figure. Good books, questionable human being. He's a Skeptic, but he's running a magazine that has been more trolly than Skeptical as of late (especially since the New York Times crawled up his ass five years ago).
I'm surprised Dan knows who he is, but I can certainly see why both a true believer and decent human being like Dan would be in conflict with a figure like Shermer.