The student protesters had been so young and carefree, he thought, he could easily have imagined himself there. Questions began racing through his mind: Why had he not learned about this before? What were the names of the victims? Was it even real?

“We were always told that this is a new era, we have left history behind and we have a good life,” Badiucao said in an interview from Melbourne, Australia, where he now lives. “But seeing the documentary made me believe that China was the same and under the control of the Communist Party, it would never change.”

Image A Badiucao cartoon of the Chinese intellectual and Nobel Peace laureate Liu Xiaobo and his wife, Liu Xia, that went viral after Mr. Liu’s death in 2017. Credit... Badiucao

Badiucao’s political awakening explains to a degree why the ruling Communist Party goes to great lengths to quash discussion of the Tiananmen massacre, which could undermine its legitimacy. Badiucao is also an example of how some young Chinese — who are better educated and expect a fairer and more just society — are willing to take action in pursuit of such ideals, as have a group of Marxist students whose fight for labor rights has run into trouble.