Definition of mental illness any of a broad range of medical conditions (such as major depression, schizophrenia, obsessive compulsive disorder, or panic disorder) that are marked primarily by sufficient disorganization of personality, mind, or emotions to impair normal psychological functioning and cause marked distress or disability and that are typically associated with a disruption in normal thinking, feeling, mood, behavior, interpersonal interactions, or daily functioning ..... So if you think that a different sexual orientation to the majority is a disruption in normal thinking, then maybe by your definition you are correct. Since we are all different, maybe we are all mentally ill?