Why does Mr. Morrison go after Uncle Hammer

Cassie tells Uncle Hammer about her visit and being humiliated yet again. Cassie is forced to apologies (twice) after being insulted and is knocked off the sidewalk by Charlie Simms. Uncle Hammer gets very angry, particularly at Mr. Simms. He mutters something about getting his gun and leaves in a car. Mr. Morrison follows Uncle Hammer and is able to talk him down. Confronting a white man would have been devastating for Uncle Hammer and the family.

To stop him from getting hurt because he is a white man and he can burn him or do anything he want‎s to uncle hammer and it will put him and his family in danger

Uncle Hammer put the family at big risk, and that was Mr. Morrison's whole job to protect them from white, racist, men.