The USA, the UK, France and Israel have shown that they can be trusted not to use nuclear bombs capriciously. I have far less trust in Pakistan and Russia.
If NK succeeds in its ambitions to develop a viable nuclear missile there is a high likelihood that it will launch a nuclear attack on the west coast of the US.
Unless NK responds to further pressure from China it may be only a matter of time before it is necessary to launch a preemptive strike. The death toll would be horrendous.
The alternative might be the loss of a major American city.