I see. I dont know the full story and based on the journalist writing this article, it looks too ambiguous. The two men barely touch their food means it's not eating and ditching . Dine and dash wasn't their intention so I can solidarity to say they left because of this American song anthem. Now, the real question is why these two men hate the anthem so much that they left the restaurant without eating their food?
One can't forget the present political atmosphere vis a vis how the US is presented to the people in the PRC by their state controlled media. In other words, the US national anthem would go over as well as a lead balloon. I had a very similar experience in the PRC once. Years ago, when the PRC first opened up to the west and many overseas Chinese were allowed to visit for the first time, I was walking on the street in Shanghai. This was 1991, at the very beginning of China's road to prosperity and 99.9% of the nation still lived in abject poverty. So whenever an overseas Chinese was seen on the streets (you could tell the difference by the way we dressed because everyone was otherwise still in Mao suits), people would literally come up to us to ask us for money to help them out. So, some old codger, I would guess he grew up around the time of the Korean war, stopped us on the street and went on a riff in Mandarin, with very nice polite tones and gesticulations. I don't really speak Mandarin all that well, so I answered him in good ole American English, whereupon his demeanor immediately soured, and he cursed my wife and I, angrily calling us foreign dogs and spat on the ground. It was like someone flipped a switch with this guy. I could only surmise that he was politically indoctrinated to such a degree that anything remotely American would trigger such a response. What's troubling about this is that the current political direction of the PRC is to garner political opposition to the west in general and to the US in particular. So having a bunch of ethnic Chinese people (it didn't matter to the visitors that the singers were legally Americans, at an American political event); singing the US national anthem would be seen as a traitorous act. I could certainly understand their rationale, even as I disagree with it. But, the restaurant owner should have called the police. It doesn't matter what the politics were, they didn't fulfill their end of the business transaction, plain and simple. Historically, government indoctrination of the populace to hate another nation's people is not new. Recall how the Imperial Japanese Army treated Chinese civilians during the war years? A lot of this had to do with just that; Japanese children were routinely and regularly taught from early age on that Chinese were worse than dogs and should not even be considered human. So to kill a Chinese, in their mind, was the equivalent of stepping on a roach.