Well, with WMDs we're past that point already. We have enough nukes to transform this world into hell in a few hours. Any advances in that area are of the nature that Putin mentioned recently, ones that no civilized nation would ever develop.

There is an enormous conventional arms market though. These are guns, pistols etc. Their sole aim is to kill people, plain and simple. You could justify it by saying some of those people deserve being killed, but as a creator of the weapon you can't know that, you have no control on how it's used. That's why many people would have moral objections against the production of conventional weapons.