It was the latest fallout in a growing dispute over a tweet by a team official supporting the recent protests in Hong Kong.
Chinese sponsors and partners have been cutting ties with the NBA after the Twitter post by Houston Rockets General Manager Daryl Morey last week supporting anti-government protests in the Chinese-ruled city.
The Shanghai Sports Federation said the cancellation of the fan event ahead of Thursday's game (local time) between the Brooklyn Nets and Los Angeles Lakers was due to the "inappropriate attitude" of Morey and NBA Commissioner Adam Silver.
A Wednesday afternoon news conference with both teams was indefinitely delayed, organisers said. Outside the team hotel, workers tore down massive banners advertising the game, according to a Reuters witness.
The Hong Kong protests were sparked by opposition to a bill allowing extradition to mainland China, but have evolved into broader calls for democracy. China has accused the West of stirring up anti-Beijing sentiment in Hong Kong. The NBA controversy also comes against the backdrop of the US-China trade war that escalated after Washington imposed visa restrictions on Chinese officials on Tuesday.
Silver said on Tuesday the league supported Morey's right to exercise his freedom of expression, further angering authorities and some fans in China and threatening the NBA's business there, said to be worth more than $US4 billion.
Morey deleted the tweet and apologised on Monday, but Chinese broadcasters, sportswear companies and sponsors have said they are reviewing their ties with the NBA, which has had a presence in China since 1992.
The NBA initially described the anger over Morey's post as "regrettable," drawing criticism from US politicians, who accused the league of putting its China business ahead of free speech.
Silver, speaking in Japan before a preseason game between the Rockets and Toronto Raptors, said it was not up to the league to regulate what players, employees and team owners said.
On Tuesday night, during a preseason game between the NBA's 76ers and the Guangzhou Loong Lions of the Chinese Basketball Association, security at Wells Fargo Center in Philadelphia confiscated signs from a couple that read "Free Hong Kong" and "Free HK." Security later removed the couple from the game after they yelled, "Free Hong Kong," a local NBC affiliate reported.
Security officials warned the couple following multiple complaints from guests and verbal confrontations with others in attendance, the team said in a statement.
"Ultimately, the decision was made by Wells Fargo Center personnel to remove the guests from the premises, which was accomplished without incident," the team said.
On Wednesday, an editorial in the official English-language China Daily accused Silver of "brazenly endorsing Morey's secessionist-supporting tweet" and giving "a shot to the arms of the rioters of Hong Kong."
"If Silver thinks endorsing the indiscriminate violence the radical Hong Kong protesters are resorting to ... is supporting freedom of expression, then he should think again," it said.
'I JUST DON'T UNDERSTAND'
Some fans expressed dismay at the way the controversy had spread, while voicing their support for Beijing's view.
"I'm patriotic of course. I support that Hong Kong is part of China, but I just don't understand this," said Yu Jie, a fan waiting to see the players in Shanghai.
The Global Times, a Chinese tabloid published by the ruling Communist Party's People's Daily newspaper, accused Silver of caving in to political pressure, saying the NBA was treating the Chinese market with disregard.
"Tweeting something offensive to the Chinese people before a series of NBA promotional activities in China only shows a lack of intellect, respect, and responsibility," it said.
Basketball is the most popular sport in China, with about 500 million people consuming NBA content. The league has deals with TV and digital media outlets across the country, and teams have played exhibition games annually since 2014.
NBA China, launched in 2008 to run the league's business, is now worth more than $4 billion, according to Forbes.
The NBA had planned media events in Shanghai ahead of the Nets-Lakers game, but Chinese organisers cancelled an event at a Shanghai school on Tuesday and an open training session with the Nets on Wednesday.
State television dropped plans to air the NBA exhibition games in China this week, saying a country's sovereignty and social stability were "not within the scope of freedom of speech."
Some Chinese fans have asked for streaming subscription refunds from exclusive service provider Tencent, which halted broadcast of Rockets games after the Morey tweet.
Online travel agency Ctrip said on Tuesday it had stopped selling tickets to NBA games and NBA-related tour packages. Smartphone maker Vivo and sportswear maker ANTA Sports Products Ltd (2020.HK) have also stopped working with the NBA.
Chinese e-commerce platforms Alibaba and JD.com appeared to have taken Houston Rockets merchandise including sneakers off their sales platforms including mobile apps as of Wednesday night.
The escalating controversy did not seem to bother some waiting outside Shanghai's Ritz Carlton hotel to catch a glimpse of the NBA players.
"Personal opinions belong to them. It doesn't affect us chasing the stars," Xu Ziyang, a university student from Jiangsu, told Reuters.
