Discuss the relationship between the Western and the African cultures as presented in The Color Purple in terms of sexism,racism, or colonialsim. For what reason is Walker critical of Western Colonialism in this novel?

Celie's sister Nettie goes to Africa as a missionary, along with Samuel and Corrine and their two children (who are actually Celie's biological children). Through Nettie's letters to Celie, we are exposed to the different cultural practices of the Olinka tribe vs. those of the African American characters living in the American South. Both seem to be patriarchal cultures. In the South, Celie and Sofia are beaten by their husbands. Celie is sexually abused by her stepfather, who she thinks is her biological father (this is how she bears the two children later adopted by Samuel and Corrine) and forced to marry Mr. __ with no real say in the matter.
Samuel the missionary, on the other hand, is more compassionate and Nettie falls in love with him and they marry after Corrine's death. Samuel is an example of a more enlightened man who does not gain power by oppressing women. In terms of racism, Samuel and Corrine, and Nettie, are in an interesting position because they are African American missionaries. They are not portrayed as taking advantage of the tribes in the same was the white colonizers are, but they are still there trying to impose a Western belief system on the tribes.
In the Olinka tribe, Nettie describes the lifestyle as a bit more idyllic that what we see in the American South, but it is clear that the tribe does not completely welcome Western influence. For example, they continue their practice of female genital mutilation. Tashi, a young tribal woman whom Adam (Samuel and Corrine's son) marries, undergoes the practice as part of her cultural tradition. This is the most controversial moment for the missionary family, as Nettie both wants to be sympathetic to Tashi and to enlighten her to the danger and oppression the practice represents, according to Western standards.