"I don't know how you extrapolate that into some sort of mental illness"

Where did I say that he had a mental illness?

Ask yourself this question. If you were on a job interview for a job where the employer was not desperate to fill that job with a "body", and you didn't have some super stupendous big deal advantage, or credentials, would you think that offering that anecdote reflected highly on you? Or do you think it portrays you a little like a slacker?