The "nasty" prime minister of Denmark. And I thought all these "Trump wants to buy Greenland" was a prank out of The Onion. Until, well until Trump tweeted he indeed wants to buy it, or wanted to.
Lesson?
If you approach a nation non-diplomatically, be prepared to receive a reply non-diplomatically too.
And when you start making enemies off your ego and feelings, this is what you end up with.