It is one thing for President Trump to try to find a deal with the North Koreans that will get them to disarm. It is another thing entirely to praise a genocidal dictator. This is completely unacceptable. The President of the United States should never, ever defend the closest modern equivalent to Hitler.
This is unbecoming the office of the President of the United States. We are to be a shining city on a hill, not a morally relativistic apologist for genocide. Some things are not worth a deal. Turning a blind eye to or serving as an apologist for this genocidal maniac are in that category.
The President will never apologize. He should, however, walk this back.