The odd thing is many of the 'spies' seem to be less driven by political ideology and more so by what I could only call being 'true believers' in reunification. Koreans culture is a very xenophobic and homogenous one, and deep down some of them want to be reunited at any cost. It's not exactly nationalism, but it is far more than tribalism.
Korea will never be happy until it is reunited. Some South Koreans can't take the strain of waiting, and seek to help the North and the South become one, no matter the price.
Most of unification-at-all-cost crowds are left-leaning. The political left co-opted the issue of unification as their own. This view is of the third world left-wing ideology, which is big on national liberation and anti-imperialist struggle.
Many do not realize that they are duped by these leftists. They think that denouncing the previous military dictatorship is perfectly OK but denouncing the N. Korean regime is anti-unification, reactionary behavior.
They also think that N. Korean regime thinks like they do on the issue of Korea and her future. Nothing can be further from the truth.