According to conservatives, the government should not make people buy insurance; it certainly should not provide coverage for them. That would seem to eliminate the two main ways to deal with free riders. One obvious possibility remains. If you can't pay for medical treatment, you can't expect to receive it. Period.
Rauch implies that libertarians face a dilemma. Either coerce hospitals to provide care to the indigent (as we do now) or coerce individuals to buy insurance.
There is a third alternative: charity. Take it as given that we feel revulsion at the prospect that someone in urgent need of medical care will go untreated. We can deal with that revulsion by a coercive system of tax collection. But we could also deal with that revulsion by contributing to charity that is dedicated to providing urgent care to the indigent. Rauch seems to have forgotten about the charity option.
All options, coercive and charitable, have the disadvantage that patients can "free ride" by not obtaining health insurance. They can count on the kindness of strangers to pay for their urgent health care needs.
The disadvantage of the charity option is that it creates an additional group of free riders. These free riders are people who want to see the indigent cared for but do not want to contribute to the charity that will make it happen.
Even granted this disadvantage, I think that the advantages of the charity option make it worth considering. One advantage is that a charity might do a better job of deciding on a fair level of cost-sharing for patients. For example, the charity might, if it deems it appropriate, pay only 20 percent of the cost of care, leaving the rest to the individual. Thus, a charity might reduce the free riding undertaken by patients.
However, the biggest advantage of the charity option is that it fits with Civil Societarianism. We need to remember that there are solutions to problems that do not require the exercise of coercive power.