So they won the genetic lottery, good for them. That's how sports work. However, you don't have men trying to get into women's sports. It's just not right. Women can try to compete with men, and no one has a problem with that. Hell, it's applauded. However, a man has an evolutionary advantage. One that is not completely negated by virtue of a sex change. You could make this argument if this was a pre-pubescent sex change, but that's not the case. We're talking about someone getting the full advantages of being a man before making the switch.
Why on earth would we have sports split by gender if the differences were so negligible or easy to overcome? Hormone therapy doesn't retard the advantage nearly enough.
The line should be drawn where it always has been. Men play with men, and women get to play with anyone if they have the skill. If you choose to change your gender later on in life, then you naturally forfeit the right to compete against the weaker gender. Why can't a mtf fighter just fight with men? Huh? What's so wrong with that? If you were born a man, you stick to fighting men. Otherwise, wait for there to be a league that allows trans fighters to engage in fair battle with one another.
I don't know why women should be forced to overcome any unnatural advantage like that. The same way we have drug testing. Sure, Cyborg has lost fights despite being a roided-up freak, but is it fair that other women should have to overcome that disadvantage? This is one of the most fundamental concepts in athletics IMO. Men are better at sports, so we don't take to embarrassing women. It's not fair and it's not fun. PEACE.