Although Julian's mother is racist—believing that African Americans ought to succeed, but only on "their side of the fence"—she is not vicious. She is condescending and wrong, certainly, but she does not have the intention to wound or to harm. Compared to her son, who absolutely is vicious and does want to make his mother suffer (and who is nice to African Americans only to upset her) she is a relative innocent, and she is compared to a child for this reason. At one point, the narrator says that "Her feet in little pumps dangled like a child's and did not quite reach the floor" of the bus. She also has a particular affinity for children, especially black children, and this seems to demonstrate some level of goodness (her behavior toward the black child on the bus is, again, condescending and misguided, but it is well-intentioned and not malicious).
The grandmother is also described as a child at the end of her story. She has had a realization, recognizing how she and The Misfit are actually more similar than they are different—she even refers to him as one of her own children—when he shoots her. The narrator says that she "half sat and half lay in a puddle of blood with her legs crossed under her like a child's and her face smiling up at the cloudless sky." She has been, again, a problematic character: she's racist and elitist and not altogether honest. However, in the end, she does seem to achieve an innocence, like Julian's mother.