The proper way to deal with this is to:
1. Tell the Doctor that what he or she is asking is crossing PROFESSIONAL BOUNDARIES, that you are not interested in answering that question, and if the Dr. insists, you will have to report them to the state medical board for political activism under the guise of a professional practice.
2. Generally, once the Doctor is told that they are crossing professional boundaries, they will desist. If they say that the AMA has indicated that the issue is health related, you should counter with the fact that the AMA is a political lobbying organization as well as a professional organization, and the "firearms health issue" comes from their lobbying arm.
3. If the Doctor is willing to talk rationally about the issue, you should be WELL INFORMED. Tell the Doctor that the "information" that he is given is very biased (so biased, in fact that the "Researchers" who did it--Kellerman, primarily, have lost federal funding, and will not submit their raw data to peer review). Ask him if the information (generally VPC type packets that say guns are evil and should be locked up behind a bank vault door) deals with safe gun handling techniques, such as the 3 Cardinal Rules of gun handling? You may just make a convert.