The story opens with Charlie Brown bitching about how he has no friends. Linus tries to console him that he's not alone, but Charlie Brown is so wrapped up loving his misery that he ignores Linus's advice that he's not the only one.
"No one likes me," becomes the theme of the story
Lucy decides that befriending Charlie Brown, a man so caught up in his own ego that he demands all his friends call him by BOTH first and last names, is worthless so she offers him some advice at a nominal price. Thus establishing that while she cares about him, he isn't going to be friend material until he gets his act together.
Lucy going above her duty then gets Charlie Brown a job directing the Christmas play. Lucy details the jobs requirements.
However, the passive-aggressive Charlie Brown goes into the play and demands everyone do EXACTLY what he says, ignoring all pleas and consensus, stating he is director so he not only deserves respect but assumes dictatorial powers.
While this is going on, Snoopy happily decorates his house. Thus, he expresses his outward joy and inspires people to feel happiness, by seeing how he decorated his doghouse. Charlie Brown sees this and instead of feeling joy, seethes with anger, at the fact that no matter how hard he tries, he isn't as creative as Snoopy and thus his own house; if he tried to decorate it wouldn't be as pretty. Thus he again misunderstands Christmas isn't a competition.
The kids ask Charlie Brown to get a tree. They are all being supportive of Charlie Brown, who is still rejoicing in his self induced crisis of misery, by telling him EXACTLY what to do and what kind of tree to get.
Linus sensing Charlie Brown may not follow direction, he goes with him. Once again, Charlie Brown says to Linus he doesn't care one hoot about anyone in the world but himself, and he'll get whatever Goddamn tree he pleases.
Of course, the kids are very disappointed that Charlie Brown failed at such a simple task. Several suggesting medication or other electroshock.
But Charlie Brown is all "boo-hoo, poor me, no one likes me." Instead of seeing all his problems as a direct result of his masochistic neurosis, he blames not himself but Christmas itself, for his misery. As if the mere holiday caused him to do whatever he wanted and not listen to anyone, then complain when they were unhappy.
Therefore, after blaming everyone from the neighborhood kids, to Santa, to Madison Avenue, Linus tells him what Christmas is about.
Linus reads a passage about how Jesus was born and concludes by saying "That's what Christmas is all about." Thus telling the TV audience that unless you are Christian Christmas doesn't apply to you. In other words out of the 7.5 billion people in the world the 5.5 billion people who AREN'T Christians don't count.
Finally, the neighborhood children sick of Charlie Brown simply decide to make the best of Charlie Brown's bad choice and of course, Charlie Brown decides to steal the decorations of Snoopy's doghouse for the tree he bought.