I agree with you.  I'm a lesbian.  I knew I liked girls since I was around 4 after seeing Catherine Bach in her Daisy Dukes.  That will never change.  I have a "preference" for the type of women I date (sporty femme tomboys who have an artistic ability like being able to draw/paint, sing, or play an instrument).  Of course I don't always adhere to that type.  It's just a preference.  If I find someone who doesn't have these qualities but is awesome in other ways then sure I'll give her a chance.  But I won't date men (or fat women, of course).