This quote by Lula is representative of the general feeling of a portion (but not the entire sum of) the Maycomb community. The feelings of oppression, resentment, social injustice, angst, and rebellion are omnipresent, but they become even more evident during the Tom Robinson trial. As Atticus Finch said, that Maycomb summer was to be hotter than ever. Not only will it be intensely awful in terms of temperature, the circumstances will also help inflame tempers already sensitive to old wounds.
Lula's words are a product of her time. Maycomb, like many other Southern cities in the 1930s, experienced a deep divide that dated back to the days of slavery. This divide was racial, social, and historical. It was a separation that had persisted for generations, to the point that even worshipping God had to be done separately.
Now, Lula's words may sound mean, but she does have a point. Her church and her congregation are also a product of her time. They existed out of the historical need for African American people, who were subjugated by a white majority, to feel safe and worship freely. Her words say that much. She is resentful and angry. All that is fair.
Still, society is not meant to operate in a divided manner. Unity is what makes society stronger. This is the lesson of this chapter. The others knew that the best course of action was to let the children in.
Zeebo, the garbage collector, for example, gracefully welcomes them. This shows that, though Lula was being divisive when she said, "You ain't got no business bringin' white chillun here—they got their church, we got our'n. It is our church, ain't it, Miss Cal?" she was only one voice amongst hundreds of others who wanted to live their lives in peace.