Weapons of mass destruction are not responsible for instigating war. People are responsible for instigating war. There are a couple of people who have made excellent points regarding this; scientific discovery and the success of a nation has always been dependent upon a oneupsmanship mentality. Saying that WMDs are responsible for instigating war is like saying that picking up a broken tree branch 40,000 years ago instigated war. They are both simply a means to an end, whether it's offense or defense.
The invention of the firearm in the Renaissance period revolutionized the previous manner of warfare and the entire world was forced to adapt. The worst and most bloody wars were fought in that period of time, as the science of war was revolutionized from standing armies into the guerilla-like tactics that were first introduced in the American Revolutionary War. A period of four hundred years passed before the military world was able to adapt to simply being able to point a hollow barrel at another person and take their life, and in the past one hundred years we've come up with far more ingenius methods of doing it than even that. The control of weapons of mass destruction is no different than the attempt to control firearms in such countries as Canada and the United Kingdom, where not even police are allowed to carry firearms because they are afraid of the general public's possession of them. Criminals will still carry the weapons, just like rogue states like Iran will be sanctioned until the end of time to shut down their centrifuges, but they will still develop weapons despite the United Nations' emphasis not to.
As for the Iraq example of WMDs inciting war, it was a scape excuse used by the Administration at the time to justify themselves initially, before other and better reasons were uncovered and solidified. Gut feelings, human instinct, and the "I KNOW it's there" mentality is what started the Iraq invasion. Human nature instigated war. The ongoing Afghan conflict has no WMDs involved at all in it, yet it continues to be one of the most involved conflicts of this day and age.
War is a necessity. A necessity deemed by thousands and thousands of years of human evolution, and before any hippies get offended -- no, other animals have not evolved to have war, but wolf packs will war amongst themselves over territory and mates, establish themselves as alpha. At a base level, the human conflicts that use swords, spears, guns, cannons, Anthrax, and plutonium are no more than advanced means of claiming territory or mates.
The regulation of nuclear weapons has been ongoing since the Strategic Arms Limitation Talks in the Cold War, followed by the Strategic Arms Reduction Treaties of the 90s. Yes, nuclear stockpiles amongst the First World have dwindled exponentially, and teh United States still holds the largest stockpile in the entire world. Not because we are better, not because we are stronger, or smarter, but because we drafted the Treaties in the United Nations with a submissive Russian Federation that had just picked itself out of the collapse of the Soviet Union. The Geneva Convention does not line out any kind of strategic arms (the cold war-era term for WMDs) limitations or any limits on the uses thereof. It is the job of the United Nations Security Council and the International Atomic Energy Agency to control the proliferation or reduction of nuclear and atomic material throughout the world.
To bring up the 'signature' use of strategic arms, the Hiroshima and Nagasaki bombings were bombings of necessity. As ZR388 mentioned, the nation of Japan would not have given up their homeland easily, and the Pentagon alone estimated more than one million American soldiers would be exterminated in an invasion of Japan, along with equal and greater numbers of Japanese soldiers and citizens. As it stands, even 65 years later, not one million people have died from the Nagasaki and Hiroshima incidents. The last time I looked, the number hadn't reached half a million. The example that Fat Man and Little Boy set was one that the Emperor respected and understood, showing America's resolve to be equal to their own, and instead of subjecting his people to further tragedies, surrendered to General MacArthur and President Truman.
The detente that occurred as a result of the arms races between the United States and the Soviet Union are what originally warped the use of strategic arms into what they are today: the greatest example of resolve and ultimate power that was to be used only as a last resort was warped into a power that has been scientifically theorized to destroy the world hundreds of times over. Now people are afraid of a nuclear winter, with the proliferation of nuclear weapons and other strategic arms as their main vessel of fear.
In conclusion, yes, I believe that strategic arms should be developed, investigated, and in certain situations used. The control thereof is a continuing aspiration, but it will never completely succeed. The next use will be not one of necessity, but one of challenge or belligerance. It is something that cannot be avoided, and the entire world will have to cope with this development of war just like it had to adjust to the advent of the firearm.