DId you hear about how Bob died? I can't believe it!
I know! Those Greasers are monsters!
When the Socs come to "give the Greasers baths" Johnny has to save him and Ponyboy before it is potentially to late.
Johnny stabs Bob because he is drowning Ponyboy. When the other Socs run away, Johnny and Ponyboy find out that Bob is dead, causing them to have to run away.
After people find out about what happened to Bob, they hate the Greasers even more, thinking that they are a danger to society.
