Okay, so I've been waiting ever since my 8 hour comment ban to cover this.
Sex is what you have in you pants, gender is how you identify and how society perceives you.
Why should what's in your pants have anything to do with your role in society?
You know what, why should gender identity have anything to do with your role in society either?
Okay back to the original subject: Gender identity is different than sex, it's that simple.