In what way is it a democratic republic? I mean, it just looks like a dynasty. If it’s not, could you explain how it’s not, and if it is, how is that ok? I’m not deliberately trying to repeat U.S. propaganda, I hope this doesn’t come off like that, but my only knowledge so far is only from the U.S., so I’m asking these questions to try to get a deeper understanding.
The US and DPRK are officially still at war. There has only been a ceasefire, but never an actual peace treaty. Also the US regularly practice “decapacitation strikes”, aka planning to to invade and murder the elected leaders in a country. That after they literally genocided a third of the population during the Korean war. So there is every reason for the DPRK to defend itself. The US isnt there to help the people, they want to get the many natural resources, and also weaken China. Also, South Korea was a military dictatorship until 1990 or so, and committed multiple massacres against civilians (check out the movie A Taxi Driver). The last president was a weird cultist and also the daughter of a previous dictator.
If you want to know more about the background, I can only recommend reading The Korean War: A History (warning, very violent at times).