All doctors treat all patients with the assumption that something could be transferred. All physicians, dentists, or who ever deals with patients fluids must adhere to infection control standards set forth by OSHA requirements. This means gloves, masks, and eye protection. If aerosols or splattering is produced, smocks and head covers are also required.
You cannot turn patients down for having a disease. The only defense this physician has is that a HT would not be recommended for this patient for "x" reason.