Not due to two deaths, due to the millions over time of their own people the regime has murdered. Due to the millions who will continue to die. And Russia and China aren't going to come militarily to the aid of North Korea, sure they'll raise a fuss but:

A. Russia and China hate each other, they'd never work together.

B. Being an ally of North Korea doesn't have enough benefit to risk war.

We need to just make it clear to North Korea that if they keep trying to start a war, there will no longer be a North Korea, only an unihabitable nuclear wasteland

Russia and China do not "hate" each other, they distrust each other and remain rivals (not enemies). But that doesn't change the fact that they do have some mutual strategic interests, and North Korea happens to be one of those. China and Russia have kept the Kims in power on the Korean peninsula because they regard the DPRK as a buffer against U.S. and Japanese military power in the region. As long as the Kims are militarily weak but unpredictable and bellicose, it keeps the U.S. from establishing complete dominance in the region.

Another problem (for China) is that if the regime collapsed, millions of North Koreans would flood China, which would have a serious economic impact and also possibly lead to civil war in the provinces which the refugees entered (Chinese in the border provinces hate Koreans already). The Chinese have enough issues with internal stability as-is.

So no, North Korea is extremely important to China and Russia, and they will go to war to keep the U.S. and South Korea out of it.

They're not trying to start a war. As I've said, when this stuff happens, it's a result of internal tensions with the regime.

Gotta try and start an internal revolution there. Too bad they grow up brainwashed.

I'm not even sure it would matter much if they didn't. Syngman Rhee (the dictator who we kept in power through the 1950s and 60s) was almost as crazy as Kim il-Sung, and he also had populist appeal. I also know a couple of exchange students from Seoul, and they say that while most of the cosmopolitan, urbanized population is pro-democracy, the rural, less educated Koreans tend to be crazy nationalist ultra-religious zealots. Exactly the kinds of people, in other words, who tend to support dictators. Even in the 1950s and 60s, the DPRK regime had a lot of support in South Korea, and their intelligence services tried to start a Viet Cong-style rebellion during the 1970s after Rhee stepped down and his successors didn't have his appeal.

What's even more ridiculous is that in spite of how long we've protected South Korea from the North, and how much money we've given them, a majority of the South Korean population vehemently hates us. If you think Europeans are ungrateful anti-American morons, you should hear what I've heard about Koreans' attitudes towards Americans.

The impression I get is that Korean culture is just naturally crazy, authoritarian, and anti-Western. And the Koreans I've talked to pretty much agree with me.

I laugh at the news when I see "South threatens retaliation if another attack happens."

This was said when they sank a destroyer with a torpedo attack, nothing happened. The south should bomb a military post in the north.

Which would have the same effect as declaring war, or escalate the situation. It would be one thing to do that if the South were sure that the North was serious about war. But at this point, the ROK's leaders understand (as do American leaders) that DPRK provocations are to be treated more like natural disasters than serious threats to national security. They're basically just something that the Kims have to do in order to politically out-maneuver their rivals to-be within the Korean People's Army.

Without sounding insensitive (because I hate dictators and human rights violators as much as anyone else), I lost a lot of sympathy for the North Koreans after I learned more about the internal politics of the DPRK. One of the things that Westerners fail to understand is that political repression usually isn't evil totalitarian regimes repressing democratic opposition. More often than not, it's totalitarians repressing other totalitarians who would be just as bad, or worse, if in power. That's how things were in Iraq under Saddam, and from what I understand, that's how things are in North Korea. In situations like that, it's a lot harder for me to feel moved.

There wasn't even much of a democratic movement in South Korea itself until around the 1970s. Part of the reason we kept Rhee and his successors in power for so long was that we knew most of the Korean population hated us and wanted an anti-American regime in power. Plenty of them also supported Kim il-Sung. We only started pressuring the South Korean regime to hold free elections after CIA analysts concluded that the democratic, Western-neutral opposition had a good chance at winning. Before that, most South Koreans probably would have been fine with an undemocratic, America-hating dictator in power.

If I was in power in a country attacks against my people would not go unpunished, all tyrants do stuff like this because they know theres no consequences, they need to be shown there is. Its stupid one side can launch attacks but the other cant since it will start a war.

I'm obviously not getting through to you. Yes, it may be bad to let the North Koreans get away with this, but the consequences would be worse, and unless the attack signifies an existential threat to South Korea's security, it's not worth the risk. There's being assertive, and there's being dumb. What you are suggesting is just plain dumb.

Fortunately, this is why people like me are in charge of foreign policy in the U.S. :D

I wish regimes like this were stopped before they became powerful.

And retaliating may be more disastrous in the short run but allowing opressive regimes to continue over time will be more disastrous.