Answer:
The author presents the contradiction between how the Chinese usually acted and instances when they could be assertive or aggressive to demonstrate that the Chinese workers were not a monolithic group with a uniform behavior, but rather a diverse group of individuals with varying personalities and behaviors. This adds to the understanding that the Chinese workers were complex individuals, not simply passive or submissive, and that their actions and behaviors were shaped by a variety of factors including personal characteristics, social and cultural influences, and historical context. Additionally, it highlights the importance of not making assumptions or stereotypes about any group of people based on limited information or observations.