I may very well reading what I want to read out of this quote, but I feel like if the quote is to be taken as a jab at non-believers, it's also a jab at believers. The "ordinary man claiming to be a skeptic" part is explicit, but note that before he claims most are incapable of both much doubt and much faith, which I think implies that the same issue goes for believers and non-skeptics.

The basic idea I'm pulling from the quote seems to be that most people won't critically think about their ideas, so you can't always trust another's self-labeling to decide if their beliefs have been well thought out.

Consider "The majority of this liquid is not water".