In the novel, John brings unprecedented fame and success to Bernard. Bernard, used to being a social outcast, and to being considered a bit of a misfit and oddball, is all of a sudden the hot guy in town, the one to be seen with, and he revels in his new role. Previously a nerd, Bernard is now popular, can have any girl he wants, and finally feels accepted in his society. Before, he put on a show of rejecting his society, of being disgruntled and disgusted by it, but it was just a front covering the fact that society had rejected him. But, with John at his side, he is the new "it" guy.
So, when John adamantly refuses to come out to the huge party that he has gathered, everyone there is upset, and leaves. It becomes clearly evident to Bernard that they were there not for his company, but to see "the Savage." The unhappy crowd completely rejects Bernard, speaking vicious and cruel things about him on their way out. Huxley does a good job of describing just how all of this impacted Bernard:
"Pierced by every word that was spoken, the tight balloon of Bernard's happy self-confidence was leaking from a thousand wounds...punctured, utterly deflated, he...began to weep."
From this point on, he treats John poorly, nurturing "a secret grievance against" him. As a result of John's refusal and the succeeding events, Bernard becomes whiney, pathetic, dejected and unhappy. I hope that those thoughts help a bit; good luck!