Silly-bad?

Each madman's epically mad:
His oddity is the ill he had.

Note for the pun-impaired or pun-resistant or simply civilized: While some of the people society calls "mad" are very dramatic about it, perhaps even epic in the scope of their madness, I'm playing here with the two epics used to describe most madness: Psychiatrists spot an oddity and define it as an illness: Hence the madman's oddity (a word suggesting "Odyssey") is the ill he had (Iliad).

The poem has another meaning, which is that one's oddities are based on past ills (not necessarily illnesses).

(Since the Illiad features the sack of Ilion (Troy), I suppose it suggests a sacro-iliac problem.)