A group of angry Chinese tourists held a “patriotic” protest after their cruise ship was delayed by bad weather, the South China Morning Post reports.

The tourists reportedly grew frustrated after their cruise ship was unable to move from a port in Shanghai because of fog, causing them to sing the Chinese national anthem and start jostling staff to show their frustration.

Yet despite the Chinese typically encouraging patriotic displays, authorities do not take kindly to the singing of national anthem in informal circumstances, as it seen as disrespectful.

Footage posted online shows customers being restrained by police before people break out in song. One man could even be heard shouting “well done” to his fellow passengers.

The vessel had been scheduled to leave for Nagasaki, Japan, on Tuesday and return to Shanghai on Saturday, although its operator Norwegian Cruise Line said that poor conditions had forced the cancellation of the trip.

The U.S.-Bermudan company that owns the operator said customers would be reimbursed through for their ticket.

A similar incident occurred in January, when a brawl erupted at a Japanese airport, leading to the arrest of one passenger, as well as a call from the Chinese embassy in Japan for customers to deal “rationally” with disputes and not let their “patriotism” get in the way of good behavior.

Last September, China’s federal legislature passed a law prohibiting “disrespect” towards the national anthem, which they define as singing parodies of the anthem, using it as background music, or playing the song during commercials. Violators now face up to 15 days in prison.

Some lawmakers have even considered banning people from holding their hands on their hearts during the playing of the national anthem, arguing the gesture is too “American” for Chinese patriots.

Such proposals are just some of a number of legal modifications debated by Chinese lawmakers in an effort to discipline people into more uniform patriotic expressions that comply with their vision of a communist China.

Official initiatives pushed by the government to promote a sense of nationalism include university propaganda campaigns pushing “patriotic hip-hop” with lyrics praising the virtues of communism and President Xi Jinping.

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