In fairness, IndyCar did not keep Danica Patrick out. Or at least they didn't in the end (I don't know the history of her entrance into that level of racing or if there was any controversy about it).
Maybe not your most central type of sport, but I certainly wouldn't argue that it wasn't a sport. Imagine if they'd said, hey, you know, this is our league, you gotta get your own league...
So my question is, why would other leagues in other sports not follow the same example (or be forced through litigation to follow the same example), where appropriate?