Why is Jem unable to speak about the trial without becoming angered in chapter 26 in To Kill a Mockingbird?

In Chapter 22 of Harper Lee's To Kill a
Mockingbird, after Atticus responds to Jem's question regarding the verdict of Tom
Robinson's trial, "How could they do it, how could they?" by
saying,

I don't know,
but they did it. They've done it before and they did it tonight and they'll do it again and when
they do it--seems that only children
weep....

Atticus's mention of children
weeping points to Jem's having trouble reconciling his childish idealism with his maturing
recognition of reality. When Scout asks about Miss Gates's seemingly hypocritical remarks about
Negroes in light of her school speech on the equality of all people, Jem becomes "furious" as he
is reminded of the terrible hypocrisy of the jury in Tom's trial. Atticus, of course, recognizes
Jem's dilemma and tells Scout that Jem is "trying hard to forget something," but Scout feels that
he is storing the incidents of the trial until he can "sort things out."