Tsk, tsk. The author has not learned. You will not change a liberal's mind with clever comebacks or even two hour arguements. No, the best you can do, particularly in today's political environment, is create doubt.
For instance, state that Obama spent Trillions to stimulate the economy...and has failed. And that failure is so profound, that he will not recover..he is a permanent loser with permanently failed policies.
I actually think the best you can do is to act incredulous when they state their beliefs, act sincerely surprised that they are so ill-informed, and then change the subject like you are trying to protect them from their own idiocy.