The Chinese have a long history of labelling those who collaborate with enemy forces as a hanjian, or Chinese traitor. One of the most infamous hanjian in modern Chinese history was Wang Jingwei, a Kuomintang politician who served as the head of a puppet state when the nation was under Japanese occupation during the second world war.
Hanjian also became a loaded term crusaders used to discredit opponents or justify what they did to them.
Hanjian has re-emerged in the media when discussing the fallout from anti-Japan protests over the disputed Diaoyu Islands, or Senkakus as they are known in Japan.
A Beihang University professor, Han Deqiang, made headlines last week after he admitted to slapping an elderly man in the face twice for blaspheming Mao Zedong during an anti-Japan protest in Beijing on September 18. He thought the man was actually a hanjian or, in this case, a Japanese collaborator.
Han, a leading leftist scholar, said he stood by his action despite criticism in the media that he had failed to observe the code of conduct for a professor.
"I'd rather go to jail than let such a hanjian wantonly say whatever he wants," Han wrote on his microblog on Sina.com.
The protests stemmed from Japan's announcement earlier this month that it was buying three of the islets from their private owner. Whatever Japan's motives, many mainlanders decried the move. Anyone who owned a Japanese branded car was deemed unpatriotic.
The line in the sand extended into sports. Li Na, the first Chinese tennis player to win a Grand Slam in the singles category, was derided for agreeing to play in the 2012 Toray Pan Pacific Open, held in Tokyo last week.
One of Li's high-profile critics has been Jia Qiang, the president of Firefly Lighting, which makes LED light bulbs in Xiamen. Jia was quoted by Tencent News as saying: "I've never watched her matches as I heard that Li Na is a hanjian. Now it's been confirmed."
Jia called upon people to burn any copies of Li's autobiography they had bought, offering to compensate them out of his own pocket.
Li's trip to Japan came after a flurry of cancellations or suspensions of Sino-Japanese events, including the celebration of the 40th anniversary of the normalisation of diplomatic ties.
A survey by Tencent of 66,700 internet users showed 82 per cent disapproved of Li's decision.
In a commentary, the Legal Daily said on Thursday that labelling Li a traitor might be excessive but her decision had nevertheless caused a rupture with hundreds of millions of people in China. "Li's decision to play in the tournament in Japan shows she only cares about her own fame. We have to say we are let down by her decision," the commentary said.
Campaigns by Jia to target Li backfired after people posted information online that indicated his company had signed three agreements with Japanese firms. It had also sponsored a firefly festival in the Philippines for five years despite the two countries' disagreement dispute over ownership of the Scarborough Shoal in the South China Seas, known as Huangyan Island in Chinese.
One prominent media commentator, Shi Shusi, said: "If we follow the logic of Jia, he is a far bigger traitor who has caused the country more harm than Li."
In a commentary carried on Sohu.com, Shi asked why patriotism led Chinese to point fingers at each other while other countries were united by the sentiment.
A China Youth Daily commentary on Tuesday warned that mainlanders were increasingly turning to incriminating labels such as hanjian, which carried powerful stigma. "Such tendency might yet cause major harm to our society if it goes mainstream," the paper said. "The ghost of radical extremism lurking behind the word requires we take it as a sign of warning and one deserving of reflection."