Why did Ponyboy snap when telling Cherry about Darry?

Towards the end of chapter 8, Cherry informs Two-Bit that the Socs are willing to play by the rules during the rumble and speaks to Ponyboy privately after Two-Bit walks away. When Cherry asks Pony how Johnny is doing in the hospital, Pony tells her that he isn't getting any better and asks if she will go visit him. Cherry responds by telling Pony that she cannot bring herself to visit Johnny because he is responsible for Bob's death, which upsets him and causes Pony to lose his temper. Pony then calls Cherry a traitor and tells her that he wouldn't want her seeing Johnny anyway. He then says,

"Do you think your spying for us makes up for the fact that you're sitting there in a Corvette while my brother drops out of school to get a job? Don't you ever feel sorry for us. Don't you ever try to give us handouts and then feel high and mighty about it" (Hinton, 110).

Ponyboy clearly resents the fact that Cherry has a comfortable, easy, secure life while his brother, Darry, works two jobs to make ends meet. He is also upset because he believes that Cherry is only helping them out because she pities them. After Pony expresses his negative emotions, he feels guilty for making Cherry upset and ends the conversation on a positive note.