Cynique and Troy - this is why I believe children's books can have a significant influence. Children in their earliest years do engage in me-not me comparisons during the development of their identity, but the judgments associated with that differentiation are culturally based. Addressing and changing these judgments which are (at least in societies arising from European domination) often rooted in Darwinism, Eugenics, and religious beliefs about gender and race is a difficult if not almost impossible process precisely because it has subtle support in the literature we offer children.
To illustrate my point, and to address the argument based on sex/gender suggested by Pioneer1 - think about the ways in which the roles of men and women are gendered. while saying "man" or "woman" doesn't evoke much other than physiological structure, the context in which the words are used is important. For example, when talking about parenthood, a man who is a parent is a "father" and a woman a "mother" - burdening what is initially a biological distinction with clearly identifiable cultural expectations and value systems regarding who should stay at home, who is more capable of nurturing a child effectively, etc.
Words carry meanings which are dependent on the context in which they are used, and once you call a person "black" or "Asian" or "Native American" you have necessarily associated that person with all kinds of cultural biases, assumptions and expectations which are often based on what we have read about these groups. It is just as hard to uproot these "racial" biases as it is to eliminate gender bias, and we must be aware of them in our reading and writing.