His comments put him at odds with the society’s official response to the dispute. In a statement earlier this month, the organization attributed the exclusion of Mr. Wong to a judgment error “at the staff level.” It also said that the organization has hosted events “with speakers representing all sides of major Asia-related issues.”

Mr. Wong was a leader of the Umbrella Movement, which began in 2014 and took its name from the umbrellas that protesters used to defend themselves from police pepper spray during weeks of widespread demonstrations where they demanded a more direct say in the election of the Hong Kong’s chief executive, its top political office.

Mr. Wong contributed to “Hong Kong 20/20: Reflections on a Borrowed Place,” a compilation of writings marking the 20th anniversary of Britain’s 1997 handover of the territory to China. The Asia Society had invited him to speak at a gathering to commemorate the publication of the book.

Once it became clear that Mr. Wong was not welcome, allegations of censorship arose, and fingers pointed at Mr. Chan, a real estate developer and philanthropist who has been outspoken in his support of Leung Chun-ying, the former chief executive of Hong Kong and the focus of the 2014 democracy protests.

“At Asia Society, we just don’t cover certain things. Can I have the liberty to do that?” the co-chairman said at the lunch on Thursday, which had the theme “Hong Kong, 20 Years Later: Promises Made, Promise Kept, Promises to be Fulfilled.”