No insurer authorized to do business in this state and to provide professional liability insurance to persons lawfully engaged in the practice of medicine or osteopathic medicine, health plans, and to partnerships or corporations lawfully engaged in the operation of hospitals, sanitariums, clinics, or other health care facilities, shall refuse to issue or renew insurance at rates which are not excessive or unfairly discriminatory as defined in Section 1852 to those persons, partnerships or corporations, solely on the grounds that those persons, partnerships or corporations have entered, or intend to enter, into valid written agreements with patients or prospective patients for the arbitration of cases or controversies arising out of the professional or business relationships between those persons, partnerships or corporations and said patients.