The South Koreans have compromised their nationalist principles in a quest for wealth and modernity, and while they're glad they did, they feel a nagging sense of moral inferiority to their more orthodox brethren. They often disapprove of the North's actions, but never with indignation, and always with an effort to blame the outside world for having provoked them.
Having worked for a Korean company and still doing a lot of business there, I think there is a lot of truth in this article. I have had conversations with Koreans who are totally oblivious - or don't really care - to the danger just sixty miles north of their capital city. In fact, most young South Koreans view America as a bigger threat to their security than North Korea. And you can point to South Korea's economic might, improving living standards and fully functional democracy for hours, but it falls on deaf ears.
Update Dec 29 - Maybe I spoke too soon, or SK finally realizes what's going on: South Korea Calls North Korea a Threat