There is nothing infantile about this. If you do not believe what propaganda says you will reveal your evil thinking eventually and this means either labour camp, prison or a bullet. There surely are people that have doubts there of course. The question is how big doubts these are and how many of such people are there. Regime like this is on the other side - the attempts to overthrow would have to reach critical mass and that is impossible. The massive long lasting famine would help change that. Lost war could do too. Nobody sane wants to risk this. The west can kill them many times over but mayhem the confrontation with them could cause is nothing the West and especially South Koreans want to try.