What Should I Have Said?

Been to a couple of doctors this week and had the strangest thing happen. Both of them went off on Bush. Today, the doctor called our President "dangerous" for his disregard for science and told me to take 100 mg of doxicycline twice a day and go see Al Gore's An Inconvenient Truth.

But the interesting thing was the other one. After explaining why the war was a mistake and how the administration's foreign policy is a matter of shame based upon ideological nonsense, he told me that he was a Republican, "not because I agree with them, but for the tax breaks." I replied that if he compared any tax advantage with the growth of his investments, since the market does significantly better under Democratic administrations, he would probably find that calculation does not turn out as he thinks. He shrugged.

What could I have said there? It is clear from his reasoning that appeals to justice or morality would be ineffective. How can one appeal to self-interest for someone who is on the fence?