In Chapter 24 of To Kill A Mockingbird, why does Miss Maudie get so angry at Mrs. Merriweather?

In Chapter 24 of To Kill A Mockingbird,some of the women in Maycomb are gathered at Scout's house as Aunt Alexandra hosts them with Calpurnia's help. Mrs. Merriweather, who Scout describes as "the most devout lady in Maycomb," (page 234; page numbers vary according to the edition), spends some time speaking about her favorite missionary activity, and then she starts criticizing Atticus without referring to him by name. Miss Maudie becomes angry when Mrs....

In Chapter 24 of To Kill A Mockingbird, some of the women in Maycomb are gathered at Scout's house as Aunt Alexandra hosts them with Calpurnia's help. Mrs. Merriweather, who Scout describes as "the most devout lady in Maycomb," (page 234; page numbers vary according to the edition), spends some time speaking about her favorite missionary activity, and then she starts criticizing Atticus without referring to him by name. Miss Maudie becomes angry when Mrs. Merriweather criticizes Atticus's defense of Tom Robinson.

While eating food in Atticus's house, Mrs. Merriweather says:

To Kill A Mockingbird

"I tell you there are some good but misguided people in this town. Good, but misguided. Folks in this town who think they’re doing right, I mean. Now far be it from me to say who, but some of ‘em in this town thought they were doing the right thing a while back, but all they did was stir ’em up" (page 236; page numbers may vary). 

Mrs. Merriweather is referring to Atticus's insistence that Tom Robinson, an African-American man, have a fair trial in a southern town that regards African-Americans as people who do not merit these types of rights. She believes that this type of action, while perhaps guided by good morals, has instead given the African-American community the wrong idea. She fears that they are "stirred up," meaning that they might start agitating for their rights. 

In response, Miss Maudie says, “His food doesn’t stick going down, does it?” (page 237; page numbers may vary). This line means that Mrs. Merriweather is eating Atticus's food happily without choking on it while she is criticizing him. Miss Maudie points out Mrs. Merriweather's hypocrisy in eating Atticus's food while speaking ill of him.