Mental disorders come in types. Autism is a hardwiring of the brain. For whatever reason, homosexuality is (stereo)typically associated with personality disorders, such as histrionic personality disorder or borderline personality disorder. Those are disorders that often develop from personal and sociological experiences, such as being bullied as a child. There's no reason that an autistic gay character should be an issue - in fact, if anything, I would think it's frustrating to the autistic community to advocate that it is. Man being PC is complicated sometimes.