The single threat to the entire human race is nuclear weapons. It is required that we get them under control or we will lose the earth as a place for humans to live.
So we must take every safe measure to reduce the number of nuclear weapons in this world.
North Korea and Iraq are examples of countries that particularly should not posses nuclear weapons because they are a threat to their neighbors. (India and Pakistan also qualify. But that is another story)
Iraq is an easily winnable war. We tried containment and inspection for a while, but it was not working, especially as certain countries like France would sell them anything including weapon grade nuclear reactors (which Israel took out) just to make a buck. So pre-emptive action, in my opinion is justified in Iraq. We may not in the end prove, or rather find, weapons of mass destruction, but they have already proven that they have SCUDs that they formerly claimed they did not.
North Korea is a different story. Pre-emptive action is NOT justified there because it is not safe, for its neighbors, and perhaps for Anchorage or even Seattle, for they already have nuclear weapons and the means to deliver them, plus a really good Army, not like in Iraq.
It is necessary for us to practice the political art of containment on NK. We did so with the USSR and they eventually came apart. But with Russia, we sent them wheat when necessary. At the same time that you contain a country, you have to make sure that its people are not so desparate that they are forced into supporting their government.
In the Russia case, at least half of its scientists were supporting the west instead of their government. That is the ideal situation. BTW-I know this from personal experience as I was once our country's liason with the Russian and East European scientists.
Where I fault Bush is that he is rying to punish the people of North Korea. That is a serious mistake. The same one has been made in Iraq, but without such serious consequences.
Again BTW (by the way) the method of containment is that if the NK were to use nuclear weapons, we would turn SK into an island.