His rhetoric toward North Korea is dangerous and irresponsible
I think his rhetoric towards North Korea serves an important purpose. Because analysts think the guy is sane, as we can see he loves the good life, Trump is reminding him that all of life ends if he gets stupid. Reminding him that he shouldn't delude himself into thinking he can start a war and survive it (much less win it), can only be a good thing. And if he's insane, he's gonna do something crazy anyway, it's only a matter of time. The other thing is, hopefully Trump's very blatant warnings will capture the rapt attention of those around NK's Kim who don't want to see their world annihilated, who might either thwart or disobey any commands to start a war akin to national suicide, or that others within NK will plot to take out this idiot who's rocket hobby might get them all killed. Note that no amount of conciliatory talk or sanctions has stopped Kim from his stunts and comments. The other groups that Trump's tough talk might positively impact are the Russians, Chinese and Iranians. None of their leadership wants a catastrophic war - and NK is becoming more and more bad for business - which both Russia and China despise. I'm not aware that Kim has ever threatened either the Russians or the Chinese - showing more so that he's not insane. The MORE Kim fears Trump, the better for the world! The less he fears him, the more likely he is to miscalculate.