Ponyboy and Johnny did not start this fight, they were just hanging out at a park on the east side, when five Socs came and invaded their territory in a blue Mustang and seemed to be looking for a fight. They got Ponyboy and were drowning him in a fountain until he blacked out (pages 42 to 45).
When the church went up in flames in chapter 6, one of the adults cries out that some of the children are missing. Ponyboy could hear screaming from inside the church. Instinctively, Ponyboy and Johnny run into the burning church through one of the windows. They find a group of terrified children at the back of the church, huddling together. Ponyboy and Johnny lifted the children out of the window. Dally yells that the roof was about to collapse. As the last child was lifted out of the window, the roof falls and Johnny pushed Ponyboy out of the window so he wouldn't get hurt. Ponyboy heard Johnny scream and tried to go back to save him but Dally knocked him out.
This is the main thing that separates the Socs with the Greasers. If the Socs were in the same situation, they would probably wait for someone else to do the job. Johnny and Ponyboy did what they thought was right and Johnny got killed in the process. This changed the view that the people had of the Greasers.
Life for the Greasers would be hard enough even without the Socs. The main part of the gang had no parents. This means that there was no one to support their education or even feed them properly. Then the Socs come along and jump them just for the fun of it, making life even harder than it already is for the Greasers. This is part of the reason of why Dally let loose in chapter 12 and got himself killed. He had already lost Johnny and nothing else seemed to matter to him. All of this also affected Ponyboy in a lot of ways; he became detached and depressed like Dally. His grades went down significantly, he lost his coordination, memory and appetite. Although Ponyboy's English teacher offered to put his grades up to a C if he wrote an outstanding autobiographical theme.
There was some sympathy that came from a few people but not from the Socs. Cherry Valance did not even want to visit Johnny when he was dieing in hospital, just incase another member of the Socs wouldn't see her with a Greaser and so it would not ruin her reputation as a Soc.