What's the best way to melt even the most racist of hearts? Why, a cute little kid of course! Carver, for all his adorable 4-year-old ways (he's dressed in a suit and a hat with a feather … c'mon!) is an important minor character. For some reason, he takes a liking to Julian's mother, "[…] looking up at her with large fascinated eyes" (83).
Of, course, Carver's mother is not amused by this. Even when she "yanks" him away, he slips out and back "onto the seat beside his love [Julian's mother]" (89). Because he's a child, he has no concept of why it might be weird or dangerous to be enamored by an older white southern woman. And because he's a child, Julian's mother gets caught up not in his skin color, but in his cuteness.
Why does he matter? We think it's significant that the ones who are most resistant to this interaction are Julian and Carver's mother. We don't know much about why Carver's mom doesn't like it (although we have some ideas; see her "Character Analysis") but we do know that Julian may not be quite as liberal and progressive as he thinks he is. It's one thing to chat up a black doctor or lawyer; it's another to cozy up to a kid.
Especially when you can tell that Julian is just terrified of Carver's mom.