Or does he just lack the normal filter most politicians have?
In an interview with the Wall Street Journal last week, Trump said Xi told him during a recent summit that “Korea actually used to be a part of China.” The comments sparked outrage in Seoul and became an issue in South Korea’s presidential race, prompting the foreign ministry to seek to verify what Xi actually said.
“It’s a clear fact acknowledged by the international community that, for thousands of years in history, Korea has never been part of China,” foreign ministry spokesman Cho June-hyuck said at a briefing in Seoul on Thursday.
https://www.bloomberg.com/politics/articles/2017-04-20/south-korea-tells-trump-it-s-actually-never-been-a-part-of-china