Whether or not you like him, the President has pretty much figured out the Kim family.
They are sort of like the Assad family in Syria.
They are really not a politically legitimate organization. They are more like a Mafia family.
They kill, torture, imprison, and subjugate their population.
If you really wanted to be “good” , and if you could, which the US clearly can, then it seems to me you would want to do something about such assholes.