Bob Sheldon is a mean drunk. He is Cherry’s boyfriend, but she is frustrated by his drinking. He is also possessive and violent.
Bob is handsome, and it does seem as if he is a decent guy when he is not drunk. According to Cherry:
"Bob was a good guy. He was the best buddy a guy ever had. I mean, he was a good fighter and tuff and everything, but he was a real person too. You dig?" (p. 116)
She describes him as having suffered family loss, and being spoiled by what he had left.
By all accounts he is very possessive, and does not want Cherry hanging around the Greasers.
Like many Socs, Bob looks down on the Greasers. He gets annoyed when he sees Cherry with Ponyboy and his friends. When Bob drinks, he gets mean and his judgment is impaired. To start the rumble, Bob insults the Greaser gang.
"You know what a greaser is?" Bob asked. "White trash with long hair" (p. 55).
When Johnny kills Bob, his death sets off a chain of events that causes the boys to run, and eventually ends in Johnny’s death.