Whether condemning the human rights records of Turkey and China or criticizing the failure of LeBron James to advocate for the Covid-19 vaccine, Boston Celtics player Enes Kanter has never been afraid to speak his mind.

The 29-year-old stoked already-simmering tensions between China and the National Basketball Association on Wednesday, branding Chinese President Xi Jinping a "brutal dictator" while condemning Beijing's policies in Tibet.

"Dear Brutal Dictator XI JINPING and the Chinese Government. Tibet belongs to the Tibetan people!" Kanter said in a message posted on Twitter, Facebook and Instagram.

"I stand with my Tibetan brothers and sisters, and I support their calls for Freedom," the Boston Celtics center added, next to a picture of sneakers adorned with Tibetan iconography and the slogan "Free Tibet".

Tibet has alternated over the centuries between independence and control by China, which claims it "peacefully liberated" the territory in 1951 and brought infrastructure and education to the previously underdeveloped region.

But human rights campaigners and exiles have accused China of religious repression, torture, forced sterilization and cultural erosion through forced re-education.

China swiftly responded to Kanter's denunciation.

By Thursday, the sports site of Chinese tech giant Tencent had pulled all upcoming Celtics games from its schedule, underscoring the uneasy relationship between the NBA and China, where the league remains wildly popular.

In 2019, Chinese state broadcasters dropped the NBA after Daryl Morey, then general manager of the Houston Rockets, tweeted a message of support for pro-democracy protesters in Hong Kong.

The fallout from that crisis continues, with Tencent no longer streaming games involving the Philadelphia 76ers, where Morey is now the president.

After criticism of the NBA's initial response to that crisis, NBA commissioner Adam Silver later clarified the league would not seek to halt players from speaking out on social issues.

"The NBA will not put itself in a position of regulating what players, employees and team owners say or will not say on these issues," Silver said in October 2019.

"We simply could not operate that way."

Boston Celtics player Enes Kanter, who has incurred China's wrath with comments about Beijing's policies in Tibet Boston Celtics player Enes Kanter, who has incurred China's wrath with comments about Beijing's policies in Tibet Photo: GETTY IMAGES NORTH AMERICA / Omar Rawlings

That stance indicates Kanter is unlikely to face any formal repercussions over his criticism of Xi and China.

Kanter meanwhile vowed to continue speaking his mind, irrespective of personal cost.

"To some people, it's money over principles," Kanter told the Boston Globe in 2019. "To me, it's principles over money."

In a 2020 op-ed for the Globe written which followed the worldwide protests sparked by the death of George Floyd, Kanter explained why he would never be silent on issues close to his heart.

"I cannot just play my game and mind my own business. This is my real life. I know that freedom doesn't come free," he said.

"In fact, the process of fighting for it has taken away everything from me. But I am determined to go on."

Kanter has previously angered the Turkish government of President Recep Tayyip Erdogan, who he dubbed the "Hitler of our century" in 2017.

Kanter said in August he was the subject of nine arrest warrants issued by Turkish prosecutors. He vowed to keep speaking out.

"#DictatorErdogan regime issued 9 arrest warrants for me. The reason behind it is me standing up for Human Rights, Freedom and Political Prisoners who are getting tortured," Kanter wrote on Twitter.

"Hey @RTErdogan. I don't care if it's 9 or 9000, I'm NOT giving up."

More recently, Kanter has spoken out against Los Angeles Lakers superstar LeBron James, who said that while he had been vaccinated against Covid-19, he did not see it as his role to advocate publicly for vaccinations.

"I was very disappointed, and it's ridiculous," Kanter said of James' stance.

"LeBron James, he's one of the faces of the league, and he should be the first one to go out there and say, 'Listen, everyone. I got the vaccine, and I'm encouraging everyone, my community, everyone, basketball fans, non-basketball fans and sports fans are just going out there and get this vaccine, so we can save other lives,'" Kanter said.

"I hope he can educate himself about this vaccination and inspire and encourage other people around him."