In Chapter Thirteen of Harper Lee's To Kill a Mockingbird, why does Aunt Alexandra get angry with Atticus?

In Harper Lee's To Kill a
Mockingbird, Atticus displeases Aunt Alexandra in several
ways.

It seems obvious that Atticus' sister believes the
children are not being brought up properly. For one thing, Scout dresses and behaves
like a boy. Atticus does not seem to mind. Soon after arriving to stay for an extended
visit, Alexandra suggests that Calpurnia, as a black woman, is not the best person to
raise her niece and nephew. Atticus will hear nothing against Calpurnia, citing the fact
that she has been with them for years, is as "tough" on the kids as a parent would be,
and is one of the family. The children love her and Atticus will not change his
mind.

Related to this is Aunt Alexandra's displeasure that
the children have been allowed to attend Calpurnia's church. When Scout speaks of
visiting Calpurnia at her home one day, Alexandra outright forbids it, and Scout is very
disrespectful. Scout is scolded by her father for her improper conduct, but Atticus does
not see Calpurnia as a black woman, but as the woman who has cared for his children as
if they were her own.

Aunt Alexandra is also very unhappy
with Atticus because the children are not familiar with their "roots." She wants them to
know the important position they are heir to in that their ancestors settled Finch's
Landing, and their "elevated" social position in Maycomb County. She wants Atticus to
familiarize them with the people from which they are descended. Aunt Alexandra also does
not appreciate the children's knowledge of their crazy relative (Cousin Joshua) who
tried to shoot the president. Atticus tries to convey Alexandra's message with regard to
their social responsibilities, but it is very upsetting to Scout because Atticus does
not sound like the Atticus they know, and it must also upset Atticus, for he tells Jem
and Scout to forget he said anything at all.