I used to get deeply involved in these type of debates. The most obvious position a liberty minded person would take is your position that a doctor should be free to discriminate, but as you have acknowledged,when you consider the system as it is the answer becomes murkier. My usual response now to these types of issues is to point out that the problems are all that result of the lack of freedom inherent in the system in the first place and thus any "tinkering" to ostensibly improve things is ultimately futile and misses the point. Debating public policy issues like these implies that we could theoretically influence the system and in that sense serves to add legitimacy to the system and prevents others from recognizing the fact that we are all prisoners.
