The north koreans are dirt poor and frankly don't employee too many intelligent folks as far as I can tell. The chinese, on the other hand, are growing rapidly, have great power dreams and will do whatever it takes to get there. It's obvious they aren't going to grow, get big, and become a peaceful democracy at this point so I am all for eliminating the problem before it starts.
I wonder if we have the knowledge of the extent of their nuclear facilities. I'm not so sure a premptive strike to destroy all of their non-conventional capabilities wouldn't be bad idea. Of course, that kind of goes against my thoughts on not isolating the international community