Point of correction:
North Korea fired missiles toward the direction of the sea off its own east coast, not towards South Korea.
Lole, Brazil (& South Africa the moment Mandela came to power) eliminated their nuclear arsenal. They figured it that they are in no danger of being attacked by other countries, and in the case of South Africa by African (frontline) countries, as apartheid had ended.
Sweden, Denmark etc. are western countries allied to the US. Period.
But North Korea has been under threat of being attacked by nuclear-armed United States, which has tens of thousands of its troops just across the border in South Korea, as well as in Japan. The US has stated that all options are on the table, meaning not ruling out attack on DPRK.
America troops in South Korea and Japan have nuclear weapons. Why not North Korea? Why double-standards? The least North Korea can do is to make sure that the American leaders think twice before attacking.
Remember former Australian Prime Minister Malcolm Fraser? He said that he doesn't want US troops stationed in his country to continue stationing nuclear weapons in Australia. The Americans responded that they need the 'right' to have nuclear weapons wherever their troops are. PM Fraser then ordered the closure of all US military bases. The bases were only reopened after the pro-US right-wing PM Howard came to power.
Remember:
Every country has the right to self-defence, and more so when you are threatened by an aggressive country which has the history of militarily invading other countries for as an absurd a reason as 'regime change' according to its (aggressor's) liking, the aggressive counry which has nuclear-armed troops just across your border.
What about nuclear arms of Israel?