If necessary, tell them that there are at least 9 professional organizations in the US that say that reparative therapy doesn't work and/or is harmful. But please pick your battles carefully, especially if it involves food, shelter, etc.
American Academy of Pediatrics
American Association for Marriage and Family Therapy
American Counseling Association
American Medical Association
American Psychiatric Association
American Psychoanalytic Association
American Psychological Association
American School Counselor Association
National Association of Social Workers
(list obtained at
http://www.hrc.org/reparativetherapy/)