Why is catcher in the rye used as a hand book for people who kill not only mark chapman but others?

I've heard others besides Chapman used "catcher" as a refrence to there miss deeds that guy who killed the actress from my sister sam had it and I know theres others but can't think of there names. I've read this book and can't find how someone could use it in this manner am I missing something? it was also used in the julia roberts/mel gibson movie consperecy theroy please won't some one explain this to me