A moment in witch one corrects another, in a more intellectual way. Weather it be in grammar, saying, quotes, or an everyday situation.
"Hey dat sweater to tight on you." To witch one would correct in a manner such as, "Sir/madam, that sweater is a bit snug, wouldn't you say so yourself?" That would be a real Mitch moment. Or when someone reads this and finds a flaw although the meaning is perfectly clear (Mitch moment).