What does Cherry tell Ponyboy in defense of the Socs?

Cherry tells Ponyboy two specific things in defense of the Socs, and they are related to each other. One thing that she tells Ponyboy is that the Greasers are not unique in having problems and rough lives. Cherry tells Ponyboy that the Socs don't necessarily have easy lives, either—they have problems too. What is amazing is that Ponyboy believes her.

"I'll bet you think the Socs have it made. The rich kids, the West-side Socs. I'll tell you something, Ponyboy, and it may come as a surprise. We have troubles you've never even heard of. You want to know something?" She looked me straight in the eye. "Things are rough all over."
"I believe you," I said.

Cherry also explains to Ponyboy what it is that she believes the Socs struggle with most of all. The Socs are kids that have so much; however, there is never a feeling of satisfaction.

"It seems like we're always searching for something to satisfy us, and never finding it. Maybe if we could lose our cool. we could."

Ponyboy is smart, and he translates her information to the heart of the issue.

"That's why we're separated," I said. "It's not money, it's feeling—you don't feel anything and we feel too violently."

The moment is a key moment of learning for Ponyboy, because Cherry is able to defend the Socs with a specific example. It's one thing for her to say that they have it rough, but this is a better defense because she can provide a concrete example.

After meeting with Ponyboy and Johnny at the movies, Cherry notices Johnny is troubled, so she seeks the story behind the boy’s demeanor. Pony tells Cherry of how Johnny was attacked and beaten senseless by a gang of Socs. The story leaves Cherry petrified, but she tries to defend the Socs suggesting that not all Socs are like that. Cherry tells Pony that just because the Socs are rich, it does not mean they don’t go through challenges of their own. Pony learns that the Socs are troubled just like he and his friends are, only that the two groups' troubles are different.
Pony thinks that it is the money that separates them from the Socs, but Cherry explains that Greasers are emotional, while Socs are forced by circumstances to ignore their feelings. Cherry suggests that the Socs are caught up in some sort of “rat race” where they are always in pursuit of something new to occupy their time but never find it.