<<Did I ever tell you the story where I jokingly asked someone if they were retarded, only to find out that they were? Talk about wishing you were somewhere else.>>
I guess in retrospect, more painful for you than the other person, who might even get a good laugh at your discomfiture, retelling the story to friends later.
Similar to a skit in an old Terry-Thomas film, TT asks this guy is he crippled, and the guy hobbles and limps around the desk and says, "Yes, actually," and then ADDS to TT's mortification by explaining, "Old war injury." The timing was impeccable.