As in a six-year-old's soccer game, there is some structure to the conversation. There are two sides, and both teams try to kick the ball as hard as they can in the right general direction. Trying to introduce a third opinion to the fray is like a confused child dribbling the ball out of bounds; the ball will be taken away from him and put back into play. The only way for a third possibility to achieve consideration is for the original game to end in defeat for one side, at which point a third opinion may be able to call "next" before the crowd's attention wanders.

If you... get into debate mode, you'll lose

Not to sound like a dick, because I'm not any good at this myself, but a skillful debater always takes the audience into account, whether the audience is the Supreme Court or a crowd of rowdy partygoers.