The note is found on the body of a ghoul wastelander in a random encounter in Fallout 3. The encounter may appear after the Lone Wanderer finishes the Tenpenny Tower quest. There are two different versions of this note depending on whether one chose to let the ghouls into the tower or not.
This version appears if the Lone Wanderer let Roy Phillips' ghouls into the tower.
This version appears if the Lone Wanderer killed Roy Phillips and his followers.
Brothers and sisters! Roy Phillips and his righteous band of diplomats have been massacred by the smooth-skins at Tenpenny Tower. It is time we arise and show the world that Ghouls are people too, that we have the same rights as everyone else, and that we won't placate and bow down to their bullshit any longer! Bring lots of firepower and righteous hatred with you. We amass at Warrington station. The revolution has begun!