Mock him all you want. This is not some tin pot dictator but the leader of the world's most powerful military by far and the world's largest economy. The North Korean leadership tried and true tactic of being erratic to elicit concessions has been met by an opponent who is even more erratic and unpredictable. The detailed description of how NK will potentially attack Guam shows they are genuinely afraid of Trump misunderstanding what they are saying.  

The Chinese have already stated that they will remain neutral if North Korea launches an attack against the US. That gives Trump "carte blanche" to drive North Korea nuts with relative impunity and he's using that to refurbish his image at home. Meanwhile, I'm pretty sure they are living anxious moments in Pyongyang. 

Little stick indeed.