While I believe that much of what Harper Lee portrayed in her novel, To Kill a Mockingbird was accurate at a point in history, I think the level of concern portrayed by such a significant portion of the white community of this imaginary town of Maycomb in the setting of the 1930s may have been exaggerated. By the time Lee wrote the book, there was a substantial portion of the country that was greatly concerned with regard to the treament of blacks in the South. However, during the Great Depression, during which the story is set, African Americans were second-class citizens, and treating them like anything but that was dangerous to white people.
Critics acknowledge that concern by Lee and others over the trials of the Scottsboro Boys in the 1930s and Emmett Till's murder in 1955 is infused into her novel, but the idea of a black person receiving a fair trial in the South was remote at best—more likely, impossible. Tom Robinson's accusers would have easily charged him with a crime he did not commit, but I believe it more likely he would never have made it as far as a courtroom.
A man like Atticus Finch might have wished to defend an innocent man like Tom Robinson, but I believe he would have avoided this in order to protect his children, if not himself. It is also rather certain that a white man would never have questioned the legitimacy of a white woman's testimony (as is done with regard to Mayella Ewell) based on what had been said by a black man (Tom Robinson). (Even in the novel, Tom realizes that expressing pity for a white woman was a dangerously insulting thing to have done.) [We see the same situation in John Steinbeck's Of Mice and Men when a white woman threatens a black man on her husband's ranch. A word from her is all it would have taken for him to be lynched.]
The historical context of To Kill a Mockingbird focuses on Civil Rights violations and the "feel" of a steady development of Civil Rights concerns in the 1950s. However, this would have been more prevalent in the North, and would not have had the strength in the 1930s that it began to experience in the 1950s and 1960s.
it was exaggerated in some ways