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As you point out, the Korean government restricts high quality 3D printers out of fear Korean people will make weapons with them.

He didn't have a 3D printer though. Just a good shop full of good tools, and the skill to use them well.

Koreans who are dissatisfied with the Korean government secretly make weapons and bombs to commit crimes.
They sneak make guns and bombs without a 3D printer. As you pointed out, Koreans who resist the dictatorship of the ruling classes have begun terrorism.

IMHO they should make solar panels, machine tools, and aquaponics instead of bombs.

I'm glad some Koreans are rebels. It may make life more difficult for some Korean people, but it is essential that people with the courage to say no to overlords resist.

Some day the empires will collapse. We will all need that spirit of independence then.