But as Asia (just realised who she is) points out - who has actually had their chromosomes tested? The doctor or midwife does just decide on a quick glance at birth.
Erm, have I misunderstood this or are you suggesting that someone born with female genitalia could still be chromasomally male 
Are you aware that genetic sex is determined at conception, it is DNA carried in the chromosome? Just wondering if that is what you think, because that is the case I can see why people have some viewpoints (like the one in the OP) that are confusing to me.
Ignoring biological sex is not a good path to go down, regardless how you feel toward your or anyone else's biological sex. You can't ignore reality or science to appease your own beliefs, this is where ignorance breeds and (think not teaching evolutionary theory in schools).
Whatever you choose to do or think about your own sex and how you relate it to your gender is completely up to you. But pretending that different sexes don't exist or don't have a significant biological impact on many factors of your life and health is a dangerous road to go down, and also completely unnecessary really.