Since Joe Gargery has been a surrogate father to Pip, he naturally thinks that Pip will be delighted by a visit from home. However, when Pip receives a letter written by Biddy, he becomes very anxious
...with considerable disturbance, some mortification, and a keen sense of incongruity. If I could have kept him away by paying money, I certainly would have paid money to prevent a visit from him.
Pip worries that Joe will disapprove of his spendthrift habits, and he is most concerned that Bentley Drummle will disapprove, not to mention Herbert Pocket, his roommate. When Joe does arrive, he is most uncomfortable because he senses that Pip disapproves of his being in London. Realizing that Pip is now a gentleman who does not wish to be associated with a blacksmith, and addressing Pip as "Sir,"Joe tells Pip he will not return,
"Diwisions among such must come, and must be met as they come. If there's been any fault at all to-day, it's mine. You and me is not two figures to be together in London; nor yet anywheres else but what is private, and beknown, and understood among friends....You won't find half so much fault in me if, supposing as you should ever wish to see me, you come and put your head in at the forge window and see Joe the blacksmith, there, at the old anvil, in the old burnt apron, sticking to the old work...."
It is this admission of social inferiority that makes Pip feel ashamed. Instead of being subservient to those of the upperclass like Pumblechook, though, Joe displays "a simple dignity" as he informs Pip that he will not return to London, but, instead, remain at the forge where Pip can visit him.
Clearly, Pip has become snobbish because of his wish to be a gentleman, feeling now that he is superior to those who do not have money and education. He is concerned with his social position, even worrying what the boorish Bentley Drummle might think if he should see Joe, who, ironically, is more of a gentleman in his heart than Pip. It is only when Joe mentions that Miss Havisham has asked him to tell Pip that Estella wishes to see Pip, that Pip shows interest in what Joe says during his visit. Nevertheless, after Joe has departed, Pip does try to catch him, but Joe has gone too far.
With Great Expectations as a satire of what Dickens considered a frivolous aristocracy, there are several targets of this satire in Chapter XXVII.