In the following months, as the epidemic in China turned into a global pandemic, Xu maintained his outspokenly critical stance. He had gained international fame in July 2018, when he published a fierce point-by-point appraisal of the Xi Jinping era and warned of the calamities that lay ahead. It was part of a series of critiques begun in early 2016 published in Chinese as China’s Ongoing Crisis: Six Chapters from the Wuxu Year of the Dog in New York in late 2019.
In early July 2020, police in Beijing detained Xu purportedly for soliciting prostitutes during a trip with friends to Sichuan in late 2019. It was a spurious charge, one often used in China to silence political critics. During his time in custody, the Ministry of Education authorized Tsinghua University to send a delegation to see Xu at the police station where he was being held. They formally notified Xu that he had been fired from the job that he had held for two decades.