What does Atticus' comment that Calprunia "...knows what she means to this family" show about his own prejudices?

Atticus loves and respects Calpurnia. She has been a mother-figure to both Scout and Jem. Atticus relies on her to guide his kids when he is not home. This shows Atticus has no prejudice in his heart. He affords the same respect to Calpurnia, a black woman, that he afforded to his late wife.