A little bit insane

Is it possible to be a little bit insane or is insanity one of those all or nothing deals? I was talking to a person recently when the conversation suddenly took an insane tangent (and we weren't even discussing religion yuck, yuck yuck!). He started going on about people being either odd or even numbers. I don't know if this was an original theory of his or something he had gleaned from one of those books in the "New Age" section of Barnes & Noble. He went on at such length that I was tempted to give the other person present a sidelong glance as if to say, "This guy's nuts, right?" Instead, we nodded politely and waited for him to finish. I quickly changed the subject and the conversation continued with no further insane flare-ups. I've had several conversations with this person before and never noticed anything odd. But the Odd and Even People Theory left its mark. Will I ever be able to have a conversation with this person again without looking for signs of mental illness? I suspect not.

Speaking of mental illness, what was the deal with the men in white coats and butterfly nets dispatched from the booby hatch to pick up the insane in old movies? Was this based on reality or one of those running gags that took on a life of its own? And wouldn't a butterfly net be rather inefficient for subduing a disturbed person? Straight jackets and rubber rooms I can understand, but not a damn butterfly net.