What did Mrs. Dubose say that made Jem angry?

Jem was angered by Mrs. Dubose's allegations and derrogatory remarks about his father (Atticus).

But Mrs. Dubose held us: “Not only a Finch waiting on tables but one in the courthouse lawing for niggers!”

Jem stiffened. Mrs. Dubose’s shot had gone home and she knew it:

“Yes indeed, what has this world come to when a Finch goes against his raising? I’ll tell you!” She put her hand to her mouth. When she drew it away, it trailed a long silver thread of saliva. “Your father’s no better than the niggers and trash he works for!”

Jem was scarlet.