I don't think the Urn of Invention analogy works.
We already have ways of creating weapons of mass destruction relatively easy and we have adjusted regulation and law enforcement to deal with it.
Consider an another analogy.
The urn of literature. We have literature which is just interesting but is emotionally neutral these are white balls.
We have literature that causes people to have emotions. These are gray balls because they can evoke people to good and bad actions.
Maybe there is a magical combination of words that will cause such strong emotions that people will commit suicide or become homicidal maniacs on mass. These are the black balls.
I hope we can agree that this is absurd. Because it is absurd for the same reason the urn if invention is absurd.... That isn't how literature or technology works.