Like a madman ... is the one who deceives ... telling a joke?"

Both the madman and the deceiver hurt people but do not take responsibility for it.

Was I not telling a joke?

The deceiver uses this question to imply that since he his joke was only for fun, he should not be blamed for any harm he has caused. AT: "I was only telling a joke." or "Do not blame me. I was only telling a joke." (See: rc://en/ta/man/translate/figs-rquestion and rc://en/ta/man/translate/figs-explicit)