I feel the important thing is to focus on subject matter and refrain from using insulting remarks just trying to "win".
A says he saw a tiger in the sky. B accuse A of "story-telling" and/or "unsound logic" w/o trying to confirm/verify the details/facts or asking how did the tiger end up in the air. And then clinging on to the mistaken belief that if the tiger can be up there, then elephants can too.
In some cases, win or not is never the key point. But throwing insults and sarcastic remarks will definitely attract further responses to disperse the accusations and insults by way of material evidences.
So, if all parties focus on subject matter right from the beginning and not degrade to insults or personal attacks and such, the discussions will end short and simple.
Simple CS T&C/guideline. Be civil.