One way the author uses irony to convey his message is By having the "winner" of the Lottery of Fairness and Benevolence punished, he shows that society is dysfunctional.
Explanation:
The complete idea of this excerpt about having a lottery with the topic of crime and punishment is a pure irony element, there are so many points of irony such as the name of the lottery "Lottery of Fairness and Benevolence" while perhaps a person who is not guilty will pay for what others have done, making the system completely dysfunctional. Then the fact that it does not matter how old the person to be punished will be, and the necessity of having soldiers around.
the author calls this the lottery of fairness and benevolence but then he describes how everyone is anxious and the atmosphere is tense. lottery's are supposed to be a good thing but here they are punishments for whomever wins them.
It is significant because a prominent leader was suggesting that the unequal treatment of African Americans was in direct opposition to the principles of the Declaration of Independence.