An example of alienation as self-protection is when Holden considers calling people, but then decides not to.
Throughout the book, Holden wants to call his sister Phoebe and others, but changes his mind. He always has a good excuse, usually that his parents will find out he is in New York.
For example, Holden considers calling an old girlfriend Sally Hayes because she sent him a letter inviting him to help her trim her Christmas tree.
Then I thought of calling this girl I used to go around with quite frequently, Sally Hayes, because I knew her Christmas vacation had started already… but I was afraid her mother'd answer the phone. (ch 9)
Even though it was a long letter, Holden considers it “phony.” He uses the fact that her mother might answer as an excuse not to call her, even though they used to be close. Throughout the book, Holden avoids phony people and therefore never really connects with anyone. Describing people as phony is just a way of avoiding getting close to a person.