system
Given the following post, respond as if you're commenting on Reddit:
human
[40k] What if the entire Inquisiton declared war against Guilliman, the Custodes and the Space Marine chapters?

The Inquisition is pissed at Guilliman, and want any above-human dead. Can they do it?
gpt
The Inquisition's already preciously thin organizational structure would crumble from within even if the Monodominants managed to acquire enough formal authority to do this. Radicals and lesser Puritans would refound the Inquisition under Imperial authority almost immediately, the Monodominants thus effectively excommunicating *themselves*. (Which, by the way, is hilarious.)

And if somehow the Monodominants managed to brainwash every single member of the Inquisition...no. They lack the necessary manpower by whole leagues. The Inquisition is a special forces and investigative body, not an army. The closest they've got is the loyalty of the Grey Knights, which is gonna get real awkward in this hypothetical.