How do we know Dally felt partially responsible for Johnny's fate?What advice did Dally give to Ponyboy on the way to the hospital after the rumble?

In chapter nine of "The Outsiders," Dallas is driving to the hospital with Ponyboy.  They are on their way to see Johnny and tell him that they had run the Socs out of the Greasers territory.  Dallas tells Johnny that he was wrong to try and keep Johnny out of trouble.  He was wrong not to teach Johnny to be hard like him.  Dallas says that if he had made Johnny act more like him that he never would have gone into the church to begin with. 

Dallas tells Ponyboy not to get attatched to anyone and not to trust anyone.  He said,

"get tough like me and you don't get hurt. You look out for yourself and nothin' can touch you..."