(1) Kim Jong-un is all bluster -- in which case calling him on it, finally ends his repeated terrorism of South Korea and extorting the world for money.
(2) He's as nutty as people think -- in which case leaving him along to build ICBM's is a threat to not only us, but the world, as he gets crazier and crazier. The only thing worse than a nut job with Fission Bombs and now reasonable means of deployment, is the same nut job with Fusion Bombs (Hydrogen bombs) and ICBM's that can take them anywhere on the globe. In which case, taking him on now, and finding an excuse to end him, or turn the world against him, is the best thing that can be done.
There's some thread the needle alternatives that have failed more often in history than succeeded. Where he's a crazy bastard, but is only bluffing when terrorizing the world, and he doesn't buy his own bullshit, and we can ignore him, and nothing bad will happen. (If you ignore that he was helping other states, possibly Iran, to develop nukes). And you hope he dies of natural causes before he does something batshit crazy. (You're betting on luck and time to make the psychopath go away -- and that the next one, won't be as bad). That's a lot of faith to kick the can down the road, and trust that your kids will better be able to handle a psycophath with hydrogen bombs and missiles to carry them, than one with far less capability. It worked so well for Chamberlain.
The good news is that whole area is being shaken awake as to the threat that Mini-Mao is to the region and world. Even if we back down, I think they're going to figure out that they better have better plans and capabilities to deal with a Nuclear North Korea. (Not just one that can set off a bomb, but actually deploy them and threaten the region, instead of just blowing himself up).
So I don't know the right answer. But ignoring the little fucktard hasn't made the world a better place for our kids. Not one little bit. It's only gotten worse in the last 60 years of that family. You're feel to free that ignoring him some more will make it better. But there's lots of reasons to believe that's not likely to happen.