I agree that it probably wouldn't be fair to let a transgender woman compete in women's mma. Personally, I think it's a terrible career choice for a transgendered woman. However, a surprisingly large proportion of people are born with ambiguous gender. Gender is not actually so black and white. At least some transgendered women really are born with some kind of a psychological difference that makes them identify as women, so while I don't think we need to go as far as to say that transgendered women should be treated exactly like most other women (because let's face it, they are physiologically very different from most women), you shouldn't be so arrogant to assume that you can fit everyone into one category or another. There are a lot of people who are born who are neither women nor men, though it's hard to generalize about them. You might want to call these people mistakes of nature, but as long as they can function in society, why should we care if they can't have children, or if they have an ambiguous or transexual nature?