It's a useful tactic in debate/rhetoric to tackle an opponent's arguments as if all of their assumptions were true, and then showing that the opponent's position is still faulty or wrong. In his manner, you don't have to convince the viewer that the assumptions are wrong, you only have to show that no matter whether they are right or wrong, your argument is still superior.
You are describing a 'civil' debate/rhetoric. We have 'left' that arena and we are now 'fighting' for the very survival of this nation as we know it. BamaKennedy has declared war against US, our life, our liberty and pursuit of happiness. He after all found half quoting Cain as his moral authority and let US know about his partnership with his god to decide who lives and who dies.