Plot hole: Guns were prohibited in the town of Big Whiskey. But in the final scene, Little Bill tells the Greeley's patrons to take out their guns and shoot Will Munny once Munny fires the last round in his rifle. A patron is even seen holding a gun after Munny shoots Little Bill and three of the deputies. According to the town ordinance, only Little Bill and the Sheriff Deputies would have had guns in that saloon, and they would not have had to be told. (01:57:00)
Continuity mistake: After getting beaten by Little Bill, English Bob doesn't have much blood on his face. The next shot of him after Bill, the blood has changed pattern and there is a greater amount. (00:45:23)
Chosen answer: I think Little Bill takes offense to this sort of thing taking place in his town on his watch. He tells Mr. Beauchamp while he is writing his biography something like, "I do not like assassins, or men of low character."