Insensitive remarks are all over the book. A lot of the book is about the conflict between two rival gangs -- the Socs and the Greasers. I recommend that you look at any parts of the book where Greasers and Socs are interacting with each other. I guarantee they will not be complimenting each other.
You could also look at a lot of the dialogue sequences where the Curtis brothers are interacting with each other. They are brothers. They give each other a hard time about everything; although, none of that is meant to be really hurtful. It's more teasing. It's the same way among all of the boys in the Greaser gang. They tease each other with a lot of insensitive remarks.
If you are looking for a specific sequence, I like chapter 2's exchange between the Greaser boys and the Soc girls.
The other one fumed around and watched us. "That's the greaser that jockeys for the Slash J sometime," she said, as if we couldn't hear her.
I had heard the same tone a million times: "Greaser... greaser... greaser." Oh yeah, I had heard that tone before too many times. What are they doing at a drive-in without a car? I thought, and Dallas said, "I know you two. I've seen you around rodeos."
"It's a shame you can't ride bull half as good as you can talk it," the redhead said coolly and turned back around.
At this early point in the exchange, Cherry and Marcia are being derogatory to Pony and Dally simply by calling them Greasers. I can almost see Marcia saying it with a sneer on her face. As if Greasers are lower than dirt and don't deserve to be in her presence. Then a bit later Marcia says this one to Dally:
Dally grinned roguishly. "I'm never nice. Want a Coke?"
She was mad by then. "I wouldn't drink it if I was starving in the desert. Get lost, hood!"
Ouch! She would rather die of starvation and dehydration than take a Coke from Dally. Now that's just insensitive.