Depicting the scene onstage illustrates the horror of the murders. Witnessing the murders makes them very real and extinguishes any empathy for Macbeth's character. The act exposes who the man has become.
Brom Bones is essentially the opposite of Ichabod. Ichabod is a weedy, scholarly man while Brom Bones is a big, physical, uneducated country "rustic." Brom is widely known as the toughest, strongest, roughest man in the country.
