Objectivity and facts
It is interesting, although unsurprising, that this comment thread once again reveals two distinct camps : the for and the against. There is no room for understanding, hardly any room for mitigation, and the against camp flings insults and disparaging comments as liberally as just about any Slashdot thread ever has.
How do you people expect peace on Earth to ever happen if you can't accept that other people's opinions may just have some basis in truth, even if it is not your opinion ?
This article says that a nuclear attack, or a conventional bombardment, is going to create a lot more deaths than any chemical attack could. Some responses contend that a man yelling "BOMB !!" in a stadium would be just as deadly due to the panic that ensues.
While that may be true, I think that the argument is a red herring. The only thing the stadium argument proves would be that PANIC is a WMD, not the man. He would just be irresponsible, or criminally insane.
One must compare things that are comparable. Any NBC manual will tell you that the lethality of a conventional attack ends at the moment the attack ends (no more explosions, no more deaths or injuries). The lethality of a chemical attack ends more or less in the seconds or minutes that follow the attack, when the active agent is either too dispersed to have any more effect, or has fallen to the ground and thus has its contact effect reduced to a minimum. The lethality of a nuclear attack ends after a few weeks, when the ambient radiation levels have gone back down to acceptable levels (outside Ground Zero of course).
Add to that the fact that, be it conventional or chemical, you more or less have to have enough ordinance to cover the area you want to target, whereas a nuclear attack never needs more than one bomb to "cover" a vastly more important area of effect.
These are the arguments that are in favor of somewhat diminishing the importance of chemicals as WMDs.
On the other hand, while a man being vaporised by a nuclear flash is something impressive, it is hardly as disturbing as viewing a person in intense pain, covered with boils and ugly skin burns, not to mention the possible regurgitations or evacuation of body fluids or matter that may accompany a chemical attack. Although I doubt that anyone posting here has actually seen a bullet wound, much less a headshot, these are concepts that are presented to us every day in the countless acts of violence liberally portrayed on TV, so we have accepted them. As for nukes, the general view outside of Japan is that such images are sought after for the thrill of seeing the flash and the fireball. Any sequence presenting the effects of a nuke (like the very good scenes in the Terminator trilogy) has a very good entertainment value, and almost no one has seen the images of the severe burns and other painful consequences of the Hiroshima survivors. It is telling that, sixty years after the event, most Japanese still have a Pavlov-type reaction to nuclear power in any form. Over there, any thing nuclear is BAD, all caps.
In short, when seeing a nuclear blast, anyone but the densest of brutes can comprehend the WMD tag associated to it. The horrors of bombardment and conventional war have also been amply described by cinematic efforts that, for the past 60 years, have endlessly attempted to bring to us the viscerality of the slaughter that is a battlefield, be it with swords and shields, or tanks and guns.
However, the chemical attack has one major difference : it attacks our body in ways that we find disgusting and disturbing. It disrupts our control of our body functions, it makes us bleed, writhe and scream, and can even modify our appearance in an impossibly painful melting process (if I rely on VX and The Rock as reference material). In other words, when witnessing the effects of a chemical attack, the level of empathy goes straight to our guts and takes an iron hold of our feelings. Do not forget that there are people that faint at the sight of a bleeding nose. The chemical attack has a terrible effect on our image of ourselves, and that makes people cringe even more.
From a technical point of view, Lewis is obviously right. A chemical attack is a nuisance to put in place, a danger to its initiator and limited in its reach. However, the effectiveness of a chemical attack is not at all on the same level as a nuclear attack.
From an emotional point of view, the chemical attack is far more disturbing on many more levels than a nuke, and that is why the international opinion rates chemicals as just as important as nukes, and that is also normal.
Besides, you cannot break down a nuke into mini-explosions, whereas chemicals can be used in specific doses following what level of mayhem you wish to create. Pop a can of lethal airborn chemicals in a metro and you'll have mass panic once the effects start showing, panic that can easily create ten times the deaths the agent will.
The chemical is just a catalyst, it is the panic that will kill most people, but that is hardly a comforting thought when you're the one gasping for air and coughing up your own lungs.