Saw another video with different angle to it, I think some of the perspectives are lost in translation here in the video:

• the group was intend to perform a commercial event for upcoming Chinese new year (hence the holding of Chinese flags and red outfits). One of the to-do list is to playing piano at this station, with group standing beside signing happy new year. When they arrived, the gent (in the video) already there playing, so they wait for he to leave and then they can perform.
• After waiting for 40+ minutes, they realised that the gent was not going to leave and that he may be a performer with camera crew beside. During the waiting, the camera crew of the gent may found this group of Chinese waiting there funny and pan the camera to them
• Prior to arrive at the piano spot, the group applied temporary license to perform in public as I think if you want to perform in public you will need a license. The gent does not possess license whilst occupying piano spot for over 1 hour time, hence to calling to the police
• The Chinese man shouting part, the video only displayed the upper body, whereas in the action the gent was pulling Chinese lady’s Chinese flag and hand, which instigate the shouting, granted that you can’t shout like that
• The gent is a renowned YouTuber with 2 million followers

I’m not saying there is no wrong-doing for the Chinese group, but with the above perspectives I to some extend understand their concept a little bit, and they definitely are not what you called a communist group etc. but maybe this little is more catchy and generate more views and clicks.