Ponyboy had never thought positively about the Socs before as he thought they were just rich and stuck up and were very different from the Greasers.
But what changes his perspective of them is that when Bob dies, he learns more about his background and who he was. He learns Bob had his own problems and was struggling just like everyone else even though he was a Soc.
Pony learns that Bob just wanted to be told "no" and be cared about, and that is how it was for a lot of Socs. Since Pony learns the Socs are struggling growing up just like the Greasers, he has a new perception of his long time rivals.
