In chapter 4 buck is disobedient. How do we know that Francois and Perrault are not cruel dog owners, but kind mailmen

Francois retaliates by bringing in a heavy club. Bitterly snarling, but remembering his lesson at the hands of the man in the red sweater, Buck stays just out of reach. Both men try to catch him, but Buck will not relent. He wants the leadership. After an hour, Francois finally throws down the club, and makes a place for Buck in front.