This simplistic article highlights numerous reasons why the US shouldn't go to war with North Korea. However whilst he illustrates why a war isn't a good idea (and it isn't) he implies that any interference in the goings on of NK is none of the USA's business, even if they do bomb Japan.
Fascinatingly enough, he quotes Santanya's well known phrase, "Those who cannot learn from history are doomed to repeat it" to illustrate his point about the mistakes of the Korean War. However, he should also imply that phrase to the Isolationist policy the US had in the 30s and early 40s which allowed a dictator far too much room to manoeuvre and almost brought about a restructuring of world order. With the new totalitarian regime possessing nuclear weapons, this is no time for America to be isolationist, and thankfully Obama seems to recognise this