I work with the Lesbian, Gay, Bisexual, Transgendered, Queer and Intersex community. Some people who identify with this group are wary of contacting a psychologist, because they may have had bad experiences in the past. This is why it is important for me to speak up as a rainbow-friendly therapist.
The way many people think is in binary categories: you are either hetero- or homosexual, or either male or female, for example. However, things like sexuality and gender exist on a spectrum, and the categorical way of thinking fails to see the full range. It doesn't leave space for, for example, bisexual or intersex people. Our brain is wired this way - by boxing and labeling we navigate more easily through the world, which can be a good thing. But categorizing people fails to acknowledge them as individuals, and so stereotyping begins.