First of all, the Hand didn't even know what to think.
Yes... They are the strongest underworld organization in the world. Yes... Nobody dares challenge them. And yes, they have the same authority as kings and queens.
Naturally, they have what it takes to make a kingdom bleed. So such an organization isn't one to take for granted.
Yet, Kent Madson did, and the implications are something nobody can even fathom. The daring nature of Kent Madson has finally made the Hand angry—and they are, in fact, very angry.
First, not only did Kent know their main goals and plans for the world, but he also knew what had to be done and what the end product would be.
If they didn't know better, they would say he was a part of them, that he was there when they discussed their plans to bring about the end of the world. They would say he had spies in their organization, and for that, they had to do a purge.