What does George Orwell 1984 show us about the nature of morality and justice in society?

This exchange between O'Brien and Winston on page 278 ought to give you an idea:

Winston: "But why are you torturing me?"

O'Brien: "Because, Winston, you didn't do your homework."

Winston: "But lots of kids don't do their homework, why are you gonna let those rats eat my face off?"

O'Brien: "Because, Winston, you are the lowest of the low. You are a liar, a thief, a sneak AND a cheat."

Winston: "How's that now?"

O'Brien: "Well, let's see, you didn't read the book, but you lied to your teacher and said you did, then you stole Andy's reply to the question and passed it off as your own. You copied everything he said, word for word, then put your name on it. And all of this in an effort to deceive your teacher and to avoid manning up and telling the truth."

Winston: "I guess I am a total and complete waste of skin, aren't I?"

O'Brien: "Yes, Winston, you are. And now this old grandfather of the sewers is going to chomp through your face and eat your tongue."

Winston: "I guess I ought to have done my homework then, yeah?"

O'Brien: "Yes, Winston, but it is too late for that now."

Winston: "AAGGGHHHRRRAAAHHH!!!"

O'Brien: "That ought to teach you, you little messer!"