I don't buy the logic, but I'll admit to not having access to the same classified material. The idea is that standing up to the West will reestablish the strength of the Kim image, and help the son take power. Moreover, there is some evidence that Kim Jong-il congratulated the
If so, it might well make the Kims the dumbest dynasty on Earth. Would it be worth it to risk war with the greatest naval powers in the world, to insure that your son takes the throne?