How do you support it is possible for the Missionary Society ladies to have so much sympathy for the Mrunas, but so little sympathy for the black- people in their own town?

I think Harper Lee includes these ladies in the story to inject some verbal irony into the story. The old ladies bemoan the plight of this tribe while they treat their own black residence with such scorn and contempt. This is the ignorance of racism that is so blatant. Even Scout, a little girl, sees the utter lunacy of these women. THese women are just so blind to their environment as well as their faith and their inner soul.

The ladies, quite frankly are hypocrites. Sadly, they can't see past the way they were raised, and they were raised with the wrong ideals and sympathies.

Just as Chapter 12 gives insight into black society in Maycomb, Chapter 24 gives insight into white women's society. Scout's experience with the Missionary Society women is somewhat mixed. She observes the hypocrisy with which the women try to do good for a remote culture like the Mrunas, but neglect the needs and sufferings of the black community in their own town. Particularly disconcerting is the way the women discriminate freely against the blacks, complaining about "sulky darkies" and making ridiculous insinuations that black men, spurred on by the trial, will start coming into their beds. The women's provincialism comes out when they speak of the Mruna people - it is evident that they have no understanding of how another way of worship could be just as spiritually meaningful as the religion they have always known. They also refuse to believe that the blacks of Maycomb are Christians, although as shown in Chapter 12, they are clearly worshipping the same God. Miss Maudie is the only woman who seems to show any appreciation for conscience, but when she speaks up, Aunt Alexandra is required by civil code to move the conversation pleasant again. Thus, the ladies never seem to discuss anything meaningful.