why is atticus so crossed with jem for what he did to mrs. dubose? what lesson about courage does he want jem to learn.

Atticus does not tolerate disrespect fro his kids especially to an old lady. Atticus wanted to explain to Jem that Mrs. Dubose had a difficult life. The yelling and insults are a manifestation of the pain and suffering that she has been through. Atticus wanted to show Jem that Mrs. Dubose is a victim of her environment and needs to be shown understanding rather than scorn. Atticus also wants Jem to look beneath her pain and see what true courage is.