[Submitter’s note: I’m referring to definition 2.]
A phrase made up by men who have failed to achieve their goals to falsely assert superiority over "lesser" individuals who they cannot create a rational argument against. In a basic sense this phrase means "nana nana boo boo, stick your head in doo doo. " The use of it is a clear sign that the speaker has a firm belief in his own ideas, and will declare that everything he says is right and everything anyone else says is wrong. Many individuals who use this type of language hold a strong belief that everything is wrong with the world, and that they are the only perfect individuals, but in reality these people are often socially-inept outcasts who still live with their parents and play Pokémon during their break at McDonald's.
John: "Corn is yellow and grows on stalks."
So-called "rationalist" : "ugh you're so fractally wrong that it defies belief, everyone knows that corn is really white but the government paints it yellow and synthesizes it in chemical saturation tanks."