The grandfather as archetype
The grandfather represents patriarchy, clearly, from his role in Hiram's family as patriarch. He represents the way that beliefs are passed down, from father to son, so to speak, but he also is archetypal in a negative way. He is a closet racist, so he symbolizes the residual damage of slavery in the South, and the perpetual problem of racism against Black people in the South. He is old school, and Hiram is happy to move away from the man's hateful and stupid opinions.
Emmett Till's salvation
The grandfather and the townspeople actively work against the Black community, hating Till for his bright personality, basically, eventually murdering him on a trumped up charge and getting away with it (because the whole community is racist, and therefore the jury also). However, Hiram himself saves Till, literally, when he's drowning in the river. This symbolizes his love for others and the value he sees in all human life, regardless of skin color.
The darkened friend
One symbolic foreshadowing comes when Hiram learns that his old friend, R.C., has become racist and violent, and he shares hateful thoughts with Hiram, assuming that Hiram will feel the same way, but in reality, he is teaching Hiram that there is more than meets the eye. He learns that perhaps people he loves and trusts might also be racist. The friend represents the unfortunate acceptance of hateful ideologies.
Reunion with the father
Another important archetypal moment comes when Hiram can look his father in the eye, understanding how much the man must have sacrificed to give Hiram a childhood free of hatred, knowing now that Hiram's grandfather was a hateful bigot against Black people, and he participated in lynching and murdering innocent people. The reunion with Hiram and his father is symbolic, because they know that they come from hateful people, and they can finally acknowledge that the dysfunction in the family is caused by the way Hiram's grandfather raised Hiram's father. Hiram respects his father now.
The kangaroo court
Hiram spends all his time trying to figure out how he can muster the bravery it will take to testify, knowing that opposing the town might mean his own death. But in the end, he never even gets called to testify. The court is a kangaroo court, because all the town is racist, so no one is willing to execute real justice, but they don't care about the lives of Black people. The realization makes Hiram feel powerless to change the situation, symbolizing the unfortunately expansive reach and scope of racism. Racist ideas are powerful in the South, he learns.
