When scout tries to tell jem about miss gates, why does he react so violently? (from to kill a mockingbird)

In chapter 26, when Scout tries to talk to Jem about Miss Gates she mentions the courthouse.  Jem grabs Scout and tells her never to mention that courthouse to him again.  Jem is still very upset about what happened to Tom Robinson.  He believed that the jury would find Tom innocent because Atticus proved that he did not hurt Mayella.  Jem's innocent outlook on life was stolen from him that day and he has yet to deal with it emotionally.  Atticus tells Scout, "don't let Jem get you down." 

The excerpt reflects collectivism, because it reveals the narrator's deep love for other individuals. hope this ! ^^