Trivia: Most movie buffs probably know this, but the mighty Mr. Eastwood is allergic to horses.
Trivia: The movie is supposedly set in early summer (July 4th and thereabout) yet autumn leaves, and at one time a morning snowfall, are seen throughout the film. The movie was actually filmed in southern Alberta during September and October.
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."