Transgenders in sports?

That's because the circumstances are entirely different. A M2F isn't the same as a F2M.

If you're M2F then you've already gained plenty of unchangeable benefits that being male gives you growing up, such as bone structure. To then take that unfair advantage into an arena that was made purely so that participants wouldn't have to deal with such oppositional advantage would defeat the entire point of female sports and you may aswell just have unisex sports at that point.

F2M on the otherhand would be someone that is disadvantaged but chooses to enter a competition with a handicap, which doesn't effect anyone else in the sport they're going into.

M2F - Unfairness against everyone else that doesn't accept it.
F2M - Unfairness to the individual that accepts it.