Cutting half of medical spending would seem to cost little in health, and yet would free up vast resources for other health and utility gains. To their shame, health experts have not said this loudly and clearly enough.
...The claim is not that there would be no harmful health effects of such a policy, but rather that harmful effects would be roughly balanced by helpful effects. And the claim is not that harmful and helpful effects would exactly balance, but rather that any net health harm will be small compared to the health gains possible by spending the savings on other health influences, and to the utility gains possible from spending the savings in other ways.
My guess is that if Robin were to try to make this argument to a general audience, he would get a hostile response. However, the opposition would be almost entirely emotional, with little or no rational component (I expect David Cutler and others who have been invited to reply will do better). The intensity of the emotions is probably a sign that Hanson is onto something.