After a lot of introspection I have realised that when I didn't accept Pansexual as a real sexuality I was just as bad as any Homophobe.
My new conclusion is that there is no SET sexuality (but they do exist). Sexuality is a huge cloud, there are parts that cloud that are Pansexual, Asexual, Bisexual, Homosexual and Heterosexual and people are usually in one part of this cloud but they may float from one to another.
I myself identify as bisexual but I'm not set on it, I tend to go through phases of Straight and gay.
Basically Sexuality is not set in stone as Straight or Gay, But can change as swiftly as the wind or be as stationary as a rock.