Question

In the short story The Weapon by Fredric Brown, why did Dr. Graham says as his reason for continuing to work on the weapon, despite the fact that it is bad for the world? Also, what does the last line of the story "only a madman “Only a madman would give a loaded retriever to an idiot!"

Answer 1

* i meant(typo) what does the last line mean?*

Answer 2

The answer to the first question is found in the story.
Dr. Graham cannot see that creating a weapon that will kill everything, regardless of the "scientific advancement" achieved, is way more "mad" than giving the gun to his son.