Jonathan CohnPaul Krugman, Ezra Klein, and Matthew Yglesias all marvel at the Republican view that (in Klein's phrase) Medicare and Medicaid cannot use studies measuring the effectiveness of different medical treatments when deciding what to cover or not cover. Yglesias formulates an explanation revolving around self-interest:

I see two ways in which it can be rendered coherent, albeit repugnant. One is basically the “welfare state for me, but not for thee” of old people. Any effort to reduce government spending on health care for the elderly is intolerable socialism, and any effort to increase government spending on health care for the non-elderly is also intolerable socialism. That’s cynical, but it also reflects the objective difference in the age structure between the parties.
Another way of looking at it is this. Currently Medicare is an unlimited commitment to pay for old people’s health care. Ultimately, that needs to be transformed into a commitment that is limited in some way. The Obama administration’s idea is to limit it technocratically, through comparative effectiveness research. The idea is that for some arbitrary level $X of taxpayer spending on health care, the funds will be allocated to the treatments with the highest cost-benefit outlook. Other treatments can be paid for out of pocket. The conservative alternative is to limit the commitment through high deductibles. The government will pay for whatever, but only if you’ve already spent $Y out of pocket. Since $Y will represent a higher share of your income the richer you are, this is a proposal that’s much friendlier to wealthy old people than to less wealthy ones.

I see explanation one as persuasive, explanation number two not so much. Even accepting the questionable premise that comparative effectiveness research will end up denying coverage for treatments that may be desirable (say, those that are slightly more effective at vastly higher cost), I don't see how ending that hurts the rich. The rich will pay for those treatments out of pocket, but the non-rich will not get those treatments at all. I don't see how that scenario should be thought of as "bad for the rich."

I think the other factor at work here is just very simply -- ideology. Conservatives do not believe that the government can rationally measure effective and ineffective treatments and steer funding away from the latter to the former. Or, rather, they begin with the premise that the market is the answer, and reject any solution that doesn't involve the market. Comparative effectiveness research is a solution to health cost pressure that involves bureaucrats. Therefore it can't work. Giving everybody "skin in the game," and assuming that patients will be discerning customers, lying on the emergency room table and requesting the intervention that makes the best use of their health care dollar, is a market solution. Therefore it will work.

Anyway, "keep the government off my Medicare" is a strong impulse among the base, and "patients, not bureaucrats, will figure out what treatments work" is a strong impulse among conservative elites. Now, conservative elites like to pretend that the base is more ideologically anti-government than it actually is. But ultimately the two strands dovetail pretty well politically.