To put NK back on the list of state sponsors of terrorism is to continue the tendency of the US to deem all undesirable behavior as terroristic. It turns the word into a political tool and divorced from reality. Terrorism is a serious issue and should be taken seriously, but not all violence, or in the situation of NK, diplomatic disagreements, fall under the umbrella of terrorism. To use the term in such a sloppy and haphazard ways only serves to make the term in the long run meaningless and to further chart a path for the central government accumulating more power.
For a good write up regarding NK and terrorism, see Micah Zenko’s 2014 writing in Foreign Policy.