Conceding that pg is right about most philosophy doesn't take away from his argument. If I conceded that most programs written in the last 5 years are garbage, would you conclude programming in general is also garbage?
"The simplest flaw in PG’s account is its scope: it implicates most philosophers up to the present"
That's what he's trying to argue with, and that is PG's claim (not that all philosophy is worthless). But then he simply concedes at the end, like he forgot his own thesis.
The biggest disagreement I see between the author and pg is the current state and value of philosophy. This is why I view the authors concession that most current philosophy might be garbage as largely irrelevant.
My "most," in other words, includes less than his.
Also, while I'm sympathetic to the intent of this essay -- easy criticism of the humanities goes back to Aristophanes -- it falls flat because it reads like a philosophy paper. A philosophy paper written in defense of academic philosophy is going to lose in the gut regardless of how correct it is to the reasoning mind (this is also why we still love Aristophanes).