Ursula Le Guin Piece

Holy cow! That's what I have to say about the piece. At first I thought it was going to be boring and poetic, then it thurned into a place of sex and drugs. Finally with all the fun and joy that everyone in the town enjoys is one boy that must sit naked in his own filth forever. What is up with that? I understand the concept of sacrifice for something good, but why do they need to sacrifice that one child. Why can't he be joyous with the rest? I know the town wouldn't be joyous if they let the child out, but why did they have to stick him in the basement to begin with? Why him? Did he do something wrong when he was younger than he already is? This piece left me with questions and confusion.