I truly think we need to follow the science on this. I understand that this makes people uncomfortable, but why be so hateful about it? There are numerous ways that biological stuff gets mixed up. You can have a person with xx chromosomes and an xy presentation. Who would ever know? Why does it really matter? This is all distraction from keeping people who do real harm from accountability (ehem, Rowling, cough, cough).
I would hope we can all see the humanity of others, the Light within each person as sacred. I wonder how many people ask WHY people want to keep them upset over this issue. Maybe it's so you don't complain about the actual inequities in pay for women in sports, or the actual problems of domestic violence...my point is there are issues far greater than this for us to worry over if we are truly interested in full equality.