Why does Miss Maudie get so angry at Mrs. Merriwheather?

Miss Maudie is angry with the women at the Missionary Circle meeting. THe women are tacitly laughing at Scout's expense,

"Miss Maudie's hand closed tightly on mine, and I said nothing. Its warmth was enough. " (Chapter 24)

Miss. Maudie also points out the hypocrisy of the women when it comes to charity. They will help the destitute in Africa while they damn their fellow black citizens. They will criticize Atticus while they enjoy his food.