I think the corruption in Gridania is deep, ancient animosity worked out from the natural order the Elementals have set. I don't think its a coodinated corruption like the Syndicate, nor is it a group, like the pirates. Its individuals with bias born from their natural system.

Think about the leaders, the Seedseers all seem like very nice people, very enlightened and despite being the arbiters of the very primal Elementals, they are worldly and agreeable to working with other nations. Heck, Kan-E-Senna actively pushed to start the Eorzean Alliance. In the guilds, while they are more simple folk, people like Luciane are opened and cosmopolitan enough to aid foreign adventurers etc. Influence pettlers, like Miounne, are also friendly, opened, and helpful to outsiders.

Really, its just the grumpy small folk, and their small ways and small perspectives. Despite being the "smallfolk" they are the most abundant folk. Whether its the small minded Conjurer initiate far removed from the level headed E-Sumi-Yan, or the surly botanist, or the superstitious villager.

Frankly, there just is no grand villainy a foot in the Black Shroud. Its just an intrinsically defensive system of governance in the that turns people off. We as players are the ones that are putting our judgments of how things ought to be onto another system. I keep seeing a cultural imperialistism towards Gridania. We "get" the government of Limsa and Ul'dah, we understand corrupt politicians and thievery and cutthroat politics. Aren't we enlightened! However, we just don't understand the covenant spiritism that guides the Shroud and it spooks us. Its different and not Western. The biggest boogy man in the Shroud, (besides the actual one in Amdapor Keep), is just backwards people. Just that simple.