Your argument seems like a form of the skeptical challenge, as it would apply to PhDs also. This makes it look less plausible though. But besides, it's easy to

Your argument seems like a form of the skeptical challenge, as it would apply to PhDs also. This makes it look less plausible though. But besides, it's easy to demonstrate that large numbers of professional philosophers are wrong by looking at the PhilPapers surveys. Mutually incompatible beliefs are held in high numbers, across the board, by many professional philosophers. Both as a group and, to a lesser extent, individuals. They can't all be right, obviously. Is a philosophy BA in a better position to make this observation than the layman? I'd say so.