It's like they take a sip to remind the Chinese of the years of humiliation endured.  Every sip is taken to communicate some kind of victorious rape.  So when the presenters of the documentary about the Chinese terracotta warriors which suggested of western influences drank their tea it was because they were feeling especially good about the evidence they just found.  They were basically telling the audience, we feel quite victorious here.  The steamy broth from China is ours now.