This is another one of those things where I think people are not doing themselves a lot of favors by criticizing Trump for taking a completely uncontroversial position. "North Korea must not be allowed to develop nuclear weapons, especially those delivered by ICBMs" is probably the least partisan opinion imaginable. Forget R vs. D. I doubt you'll find another country other than North Korea itself that would actually support the creation of nuclear North Korea. Trump's tweet, while aesthetically inelegant, is exactly in line with the position of the Clinton, Bush, and Obama administrations.
Of course, the hard part is figuring out how to stop North Korea from advancing its nuclear and missile programs without getting a bunch of people killed, and that's where Trump can royally #### things up. But his tweet is just reiteration of longstanding US policy.