Only a brief answer is possible to this complex question. Both Marshall's parents had profound and individual effects on Marshall's character and qualities as an adult. While William Marshall taught his son to stand up to racism in Baltimore, their hometown, and to respond to any racist remark from a white person "immediately and directly," Norma Marshall was refined, sophisticated, charming, an avid reader and played the piano. While William influenced him to be assertive and not looked down at the feet of any white man, Norma taught him to take his intelligence and natural grace as far as they could get him (and they got him to the Supreme Court).
An incident in Marshall's early career as a lawyer in Baltimore illustrates the impact his father's teaching and quality traits had upon him. After the infamous Atwood lynching, Marshall, a lawyer in his first job for only a week, was part of a group invited to a meeting with the Governor. During the meeting, Marshall stood up and asked the Governor the very direct and pointed question of whether, in racist and segregated Baltimore, an investigation into the lynching of Atwood was being conducted by the State Police department. The Governor declined to respond with anything but by saying that he could not compromise ongoing police proceedings. This incident shows the powerful effect his father's insistence that his sons not give in to racism but answer it directly and immediately was carried forward into his adult life.
Although Marshall was the youngest lawyer in the room, he asked the most pointed question, using a poised assertiveness that would appear throughout his career. "Is there an investigation taking place in the state police department?" ... Marshall spoke up and asked the governor a very direct question, providing an early glimpse of the advocate who would fundamentally alter American history.