A madman is treated as one absent. [ Coke ]

A madman and a fool are no witnesses. [ Proverb ]

Ne'er put a sword in a madman's hand. [ Scotch Proverb ]

A madman is punished by his own madness. [ Law ]

As much wit as three folks, two fools and a madman. [ Proverb ]

The dreamer is a madman quiescent, the madman is a dreamer in action. [ F. H. Hedge ]

I won't rule out direct talks with Kim Jong Un, I just won't. As far as the risk of dealing with a madman is concerned, that's his problem, not mine. [ President Donald Trump, Gridiron Club's 133rd Anniversary Spring Dinner, March 3, 2018 ]

He that is proud of the rustling of his silks, like a madman, laughs at the rattling of his fetters; for, indeed, clothes ought to be our remembrancers of our lost innocency. [ Thomas Fuller ]