When the North Korean government does not have what it needs, it depends on the rest of the world to supply it on charity. When this is not done North Korea threatens to attack South Korea. The situation in North Korea is bad, and it won't improve without sanctions. North Korean leaders need to give up power and yield to South Korea, and allow a single Korea to be formed on the South Korean example. Generally public opinion supports sanctions on North Korea.
North Korea has been treating its people shamefully for decades. It has taken time for this information to filter out because it is so locked down, but the world is now at least marginally aware of North Korea's abuses. Starvation is widespread. The state controls everything and deals with even faintly dissident people most harshly. If we trade with this country and recognize its status diplomatically, we grant tacit approval to its cruelty. This would be wrong. Until such time as North Korea begins treating its people with respect and stops the rampant violation of human rights, we should impose sanctions, and public opinion supports this.