I have better things to do than try to argue Korean politics in Hacker News (and I have a hard time keeping my voice calm with this), so I'll just point out a few obvious points, for posterity.

Park Chung Hee was drinking whiskey with his aides, a singer, and a girl "recruited" by special services, while talking about rampant protests that were sweeping the country. One aide, Cha Ji-chul, had reportedly said a few days eariler: "Cambodia killed three millions. Is it a big deal if we kill a million or two?" Mind you, he was talking about the particular wave of protest that was sweeping Park's own political base, the Southeast (Gyeongsang) region[1].

Probably fearing that Cha and Park were serious, another aide, Kim Jae-gyu, shot them in the party scene (Oct 26, 1979), thus ending more than a decade of dictatorship.

South Koreans finally had a chance of democracy, which my fellow Korean here referred to as "a major state of chaos". Unfortutely, during the hectic moment, another general, Chun Doo-Whan, staged a coup on December 12th, gaining power.

Of course South Koreans throughout the country didn't like it a bit. There were massive protests everywhere, including Seoul, which is (somewhat poetically) called "Seoul's spring on 1980". This is what it looked like [2].

Nobody will know exactly what was in Chun's mind, but he might have thought that he should make an example, probably not Seoul itself (too dangerous: he probably didn't want to murder people right in front of the US embassy's eyes) but big enough that people would take notice. A "strong response" to "stabilize the country", indeed.

The rest, as they say, is history.

While Chun was in power, the May 18th massacre was officially called "Gwangju incident (광주사태)", and the official version was of course that communists infiltrated the city of Gwangju, started a revolt, and the soldiers put things back to order. Stories and gruesome pictures of people shot on the street and flattened by military vehicles slowly circulated, with angry whispers in low voices. When a university student, Park Jong-chul, was tortured to death in 1987, people finally decided they had enough, which ignited the June 10th movement [3].

"Bring Park Jong-Chul back to life!" they shouted. "Murderer Chun Doo-Hwan, step down!"

Sure, South Korea is a free country. If you want to claim these hundreds of thousands of people were mislead by communists, go ahead. But it's thanks to those people who stood against soldiers and militarized police, in the street of Geumnam-ro in Gwangju or in front of Myeongdong Cathedral in Seoul, that I or you can say what's in our mind without fearing imprisonment, torture, and death.

* There was no happy ending. On June 29th, the government finally relented, promising a popular election for the next president. Unfortunately, because of an age-long feud between two opposition leaders (Kim Young-Sam and Kim Dae-Jung), they both entered as candidates in the election, resulting in Chun's minion, Roh Tae-Woo, becoming the next president. Several years later, Kim Young-Sam did one of the worst about-face in South Korea's short political history, and joined Roh Tae-Woo's party, creating a mega-party that basically surrounded Kim Dae-Jung's Southwestern region, and basically cementing the Southeast region as the bastion of conservatism for decades to come.

(It's slowly changing these days, though.)

[1] http://ko.wikipedia.org/wiki/%EB%B6%80%EB%A7%88%EB%AF%BC%EC%...

[2] https://www.google.com/search?q=80%EB%85%84+%EC%84%9C%EC%9A%...

[3] https://www.google.com/search?q=6+10+%ED%95%AD%EC%9F%81&&tbm...