In the first instance strong messages are best conveyed in face to face meetings between diplomats or presidents. This is what the Chinese government might reasonably expect and respect. Off the cuff remarks or, even worse, tweets, might cause misunderstandings or rapid military escalations. Both Trump and Tillerson are used to bullying people in the course of business activities. However, international diplomacy is not quite the same as business. I for one would be extremely upset if an insomniac initiated WW III with a series of ill advised tweets at 3 am.