While all of the other prominent tycoons in Hong Kong have stayed silent about the protests or issued statements filled with Communist-style jargon about the need to “resolutely stop the turmoil,” Mr. Lai has not only supported the protesters but has also joined them.

“The establishment hates my guts. They ask, ‘Why don’t you just let us make money in peace?’ They think I’m a troublemaker,” he said, adding: “I am a troublemaker, but one with a good conscience.”

He has caused further anger by cheering on President Trump, whom he describes as “the only one who plays hardball with China. This is the only thing that China understands.”

Born across the border in Guangdong Province, Mr. Lai fled to Hong Kong in a boat as a boy and was a typical success story in the then British-ruled city. He stayed away from politics and diligently worked his way up from lowly jobs as a knitter to become the main owner of Giordano, a successful chain of clothing stores.

The 1989 Tiananmen bloodshed, he said, made him start thinking about politics and led to his setting up Next Magazine the following year, a move that quickly hurt his clothing business once he started writing insulting articles about leaders in Beijing.

“I had always hoped that China was changing and would become a democracy. I was wrong. It was wishful thinking,” he said.

In retaliation, the Chinese authorities began closing his Giordano clothing stores on the mainland. He realized he had to either sell or mind his tongue. He sold everything but his media holdings for nearly $320 million.