Following the deaths of Johnny and Dally, Pony has been going through life in a daze. His grades have suffered and he is in danger of failing at least one class. He has stopped eating ("Everything tasted like baloney"), and Two-Bit is worried that Pony will try to adapt Dally's motto to "Get tough"--nothing can touch you then. When Pony joins Two-Bit and Steve in the school's back parking lot, they are approached by a carload of Socs. Three of them get out, and they recognize Pony as "the guy that killed Bob Sheldon." But Pony feels no fear or anxiety when he faces the three boys by himself.
I wasn't scared. It was the oddest feeling in the world. I didn't feel anything--scared, mad or anything. Just zero.
Pony discarded his cigarette and broke off the end of a nearby pop bottle. When he hopped off the car on which he had been sitting and threatened the Socs, "they got into their car and drove off."
Ponyboy changed throughout the story and now he grew touch but two-bit told him not to.
The reason is because he changed over the course of the book. He is willing to get tough over Socs since his friends died making him more dark.