The fact that Ralph calls the boy Piggy even though he asks him not to shows that people tend to pick on the weakest members of society, even if they have a lot to contribute.
Piggy is one of the most valuable members of the island community. However, his contributions are continually discounted because the boys undervalue his worth due to his size and his physical condition. They bring the prejudices of the mainland with them.
When Piggy first meets Ralph, the boy who is chosen as leader by the others due to his beauty and physical prowess, he specifically asks Ralph not to call him Piggy. That was the insulting nickname the other boys used to call him at home due to the fact that he was fat. He hated it, and he can’t wait to escape it with these new boys. However, Ralph loves the name and immediately thinks it is funny.
“I don’t care what they call me,” he said confidentially, “so long as they don’t call me what they used to call me at school.…They used to call me Piggy.”
Ralph shrieked with laughter. He jumped up.
Piggy clasped his hands in apprehension.
“I said I didn’t want—” (Ch. 18)
Ralph is not sympathetic to Piggy’s plight, and does not get any more sympathetic when he learns that Piggy is asthmatic, saying, ““Sucks to your ass-mar!” (Ch. 18). He is not necessarily a bad person, but he is immature and way over his head as a leader. He does listen to Piggy when he tells him how to blow on the conch shell, and that is how they get all of the boys together. It's a completely unintentional cruelty, which makes it both better and worse. Ralph is wrapped up in his own selfish superiority.
Poor Piggy never has any other name, because when Ralph introduces him to the other boys, this is the name he uses.
Jack is even crueler than Ralph, calling Piggy “Fatty” and telling him to shut up. Ralph is coming to his defense, in a way, when he tells the boys that his name is actually Piggy. However, what it does is make Piggy an outsider.
“He’s not Fatty,” cried Ralph, “his real name’s Piggy!”
A storm of laughter arose and even the tiniest child joined in. For the moment the boys were a closed circuit of sympathy with Piggy outside... (Ch. 1)
This incident shows that kids, and people, will often sink to the lowest common denominator—find the person you can pick on, make him feel bad, and then everyone can come together based on that. Society has been doing this, and continues to do this, since we lived in caves. Will we ever evolve past it? Who knows? It is horrible behavior. The children, once removed from civilization, create their own civilization on the island that mimics the one they left.
This book has become synonymous with the dark side of human nature. We like to think that children are innocent. The things they do to each other, then, must come from what is innately inside of them. However, Ralph is not a bad person. While Jack might represent the baser parts of our nature, Ralph represents our desire for order. Even though he does treat Piggy well, he does not victimize him on purpose. You can be cruel unintentionally.