In A Gathering of Old Men, what do you think of Mapes’s tactics when he questions and strikes the black men, and why does he behave this way?

After driving up the dusty road and arriving at Mathu's place, Sheriff Mapes steps out of his squad car in his gray suit with a red tie. He assesses the situation and then questions the old men, employing the tactics of a sheriff in the South of a former day: He seems brutal and bigoted. 
In Chapter 8 of A Gathering of Old Men, the old black men walk through the graveyard in a symbolic gesture of their remembrance of loved ones who died dissatisfied or were harmed under the cruel feudal-like system of the South. They then enter the yard of Mathu with fervor and a new resolve to assume the blame for the death of the Cajun Beau Bauton, and, in so doing, assert the manhood they have sacrificed in the past.
When Sheriff Mapes arrives in his squad car that is shrouded in a cloud of dust, the burly man steps out, looks around, and asks what has occurred. Candy insists that she killed Beau; however, the sheriff looks at Mathu, who remains quietly squatting on the porch. Since there are yet residuals of the methods of the Old South, Sheriff Mapes slaps the almost eighty-year old Uncle Billy and others that he interrogates when they each claim responsibility for having shot Beau.
Even in the 1970s and later, sheriffs wielded much power, and on this day Mapes is brutal. Furthermore, he knows these old men have compromised their manliness in the past because of their fears of "the man" when racial cruelty was allowed. Therefore, he hopes to intimidate them in a similar fashion and learn who is the real perpetrator of the murder.
Mapes's brutish behavior suggests that he does not truly care what precisely has occurred; he simply wants to find the culprit and arrest him before Beau's father Fix hears of the death of his son and further conflicts develop. Mapes's desire overrides any real investigation of the motives and details in connection to the death of Beau demonstrate the sheriff's desire to preserve the status quo.