Consider the following quotes from the first few pages of the story.

The air smelled of rotten melon. A few flies kept buzzing above the couple's lunch.

[...]

In the center of the square stood a concrete statue of Chairman Mao, at whose feet peasants were napping with their backs on the warm granite and with their faces toward the sunny sky.

[...]

The Cultural Revolution was over already, and recently the Party had been propagating the idea that all citizens were equal before the law.

Ha Jin sets the stage for his story with stunning visual and olfactory imagery. The rotten smell and presence of flies highlight the prevalent social malaise and dysfunction in Chinese society. Although the Cultural Revolution is over, there is little indication that the common people have reaped any practical benefits from it. Peasants sleep at the feet of Mao's statue, a fitting symbol for their continued oppression. By all accounts, the Cultural Revolution was an abject failure. It led to the deaths of millions of Chinese people. Some experts estimate that up to eight million people may have perished during Mao's terrible revolt against capitalism.

To meet his aims, Mao mobilized the Red Guards, a powerful student-led paramilitary movement. The Red Guards terrorized both common citizens and Communist Party members. Many victims were tortured and murdered for suspected loyalties to bourgeoisie ideals; none received fair trials.

"You must compensate me for the damage and losses. Don't mistake me for a common citizen who would tremble when you sneeze. I'm a scholar, a philosopher, and an expert in dialectical materialism."

[...]

"Now, you have to admit you are guilty," the chief said. "Although it's a serious crime, we won't punish you severely, provided you write out a self-criticism and promise that you won't disrupt public order again. In other words, whether you will be released will depend on your attitude toward this crime."

In the above quote, Mr. Chiu finds himself in the same predicament as a common citizen. He is powerless against the false accusations levied against him.

Interestingly, Mr. Chiu also maintains that he is an expert in dialectical materialism, an ideology developed and championed by Friedrich Engels and Karl Marx. The phrase "dialectical materialism" is a difficult one. The first word, "dialectical," refers to how opposing forces impact each other. Meanwhile, the second word, "materialism," refers to the Marxist belief that the world has an objective or separate practical reality from the things of the mind.

Dialectical materialism is a Marxist philosophy centered on tangible actions, particularly revolution. Marxists believe that the common people (proletariat) and elites (bourgeoisie) can exist only in conflict with each other, due to differing perspectives about society. They posit that revolution (dialectical opposition) must be the only answer to this conflict. Additionally, the goal of a revolution should be to decide who will ultimately hold the reins of material production.

Ha Jin highlights Mr. Chiu's experience to make a point: a revolution spearheaded through totalitarian means does little to promote actual personal freedom.

Fenjin was baffled by his teacher, who looked ferocious and muttered to himself mysteriously, and whose jaundiced face was covered with dark puckers. For the first time Fenjin thought of Mr. Chiu as an ugly man.

We might consider this quote an indicator of change in Chinese society, represented by Mr. Chiu’s actions. Previously, Fenjin admired his teacher and saw him as someone he could learn from. However, his stint in jail as a wrongfully accused saboteur has made him bitter and resentful. With no tangible way to get revenge on the bystanders or the police themselves, Mr. Chiu seeks to spread his contagious hepatitis. The corrupt system has impacted him and made him ugly in Fenjin’s eyes.