The original OP was not adressing things that can have a dialetic good/bad use like a knife, but things that can only have a bad effect, like guns for instance,

The original OP was not adressing things that can have a dialetic good/bad use like a knife, but things that can only have a bad effect, like guns for instance, they will only be used to hurt or take lives, you cant cook with a gun.. In his manhattan project example, produce atomic bombs will have only one bad consequence, same with guns, but not the same as a knife.