I am an attorney, but this is not my area of law; that being said, this did not sound proper or ethical to me as presented. I do know that a doctor can refuse to take on a patient, if for instant they might believe the patient was manipulative or drug seeking.
If this patient is a current patient, there are certain guidelines, and I found a link which sets forth the many circumstances and reasons, some regarding ability to pay, some regarding how difficult the patient is, etc...
The article goes into a lot of detail but I believe that the last two paragraphs summarize it best and I would not want to be the attorney for that practice, if they are going about it in this manner:
"In summary, the physician/patient relationship, which is similar to any contractual relationship, creates certain obligations. Assuming that a physician/patient relationship exists, a physician has a duty to treat and may not just say "no" to care of a patient without exposure to liability for abandonment of the patient and possible malpractice. A physician’s withdrawal from the relationship should not be attempted or accomplished during a time when the patient is in need of medical attention.
In every other instance, prior to withdrawal from or termination of the relationship, the physician should explain to the patient the reason why the physician is unable to attend to the patient’s needs and assist in the patient’s transfer to a competent substitute. Written documentation of the physician’s notification to the patient and of the referral sources or providers recommended to the patient will demonstrate that the physician has satisfied the conditions for proper withdrawal. Just as the physician must exercise reasonable care and skill in treating the patient, the physician must exercise reasonable care and skill in discontinuing the physician/patient relationship."