I'm not sure that I lend much credence to the idea that Charlie is a Stupidworlder, but whether or not that's true, he IS an anomaly among Erfworlders.
Charlie is one of the only Erfworlders who doesn't approach things in a direct fashion. Erfworld runs on war, completely; the very concept of a "bubble side" like Faq that does not itself engage in war is an anomaly, one that probably doesn't last especially well (considering how perfectly set up to allow it Faq was, and how rare that confluence of factors is).
Charlie and Parson are, arguably, perfectly opposing forces. The Thinkamancers fear Charlie for the same reason the Hippiemancers protect Parson: Charlie and Parson each represent a force capable of radically altering the very nature of Erfworld.
Charlie represents a side with extreme "control" capability, making him virtually impossible to attack. Just getting to his capital undetected would be borderline impossible, and assaulting his absurd defenses, backed with that many Archons, would be more or less suicide for even a force the size of the first Royal Crown Coalition. From the sounds of it, an allied force the size of the first RCC is both rare and prone to not lasting longer than its initial purpose; the first RCC army was held together pretty much entirely by Ansom's charisma, and I doubt you're likely to find a warlord with the charisma to keep a force that big together on the march against Charlie.
Thus you have one guy who has an absurd amount of defensive capability, who can also find and sneak-attack and raze anything you leave without a huge garrison, who can also exert an incredible degree of influence over the course of events in a gigantic area with just the Arkendish and maybe a couple Archons to serve as focal points. This is an incredible, incredible amount of power, enough that Charlie arguably could eventually "win" at Erfworld. Make no mistake: the Thinkamancers are not in error here! Perhaps the only other "destabilizing" force this significant are the Arkenpliers, and while those are powerful, their power is only great within the bounds of standard Erfworld combat. They don't allow one to break free from the standard paradigms of Erfworld combat and fight the entire damned world on a field of their own making like the Dish does.
On the other side, you have Parson... literally the only person on Erfworld who would be able to figure out a way to break Charlie's power, and the only person on Erfworld other than Charlie who stands a chance at breaking the "game" enough to bring an end to the constant wars on Erfworld.
In my estimation, based on what has been shown of Erfworld mechanics, it is literally impossible for a Side to expand beyond a certain point, and the "rules" of Erfworld are engineered to make it impossible. Which is why Parson's talent-breaking the rules-is so incredible here.