The point of competitive sports is to allow people to show that their talent, their drive and their spirit can conquer adversity. To allow Semenya to keep the gold medal does a disservice to every woman who participated in that event.

Semenya is a hermaphrodite, not a woman. If we are simply talking about social interaction and gender identity, Semenya can choose a gender and stay with it. If Semenya wants to identify as a woman, then "she" is free to do so regardless of biology. She can have further surgery if she feels it necessary.

However, we aren't talking about simple matters of gender identity. We are talking about (1) a birth condition that her parents were likely aware of, (2) a physiological advantage that is a disqualifying factor by the rules of the competition and (3) at least an inference that someone, somewhere knew or should have known that this might have been a factor yet chose to conceal it.