In reply to Chris the Tall:
> So unfortunately it may be necessary to pick a demarcation line that is unfair to a few, in order for it to be fair to the majority
Utilitarian attitudes like this always discriminate against minorities. Taken to their extreme, they result in authoritarian regimes run for the benefit of the majority who are considered 'normal'.
Pure application of utilitarianism does not sit well with other, equally important considerations for our society such as inclusivity and equality.
It's easy to say 'for the greater good' when you're not the one being forced to take hormone supplements to make you more like society expects you to be.
Equally, sport relies on a level playing field in order to retain our interest. People quickly switch off from sport where one team always wins easily.
So I don't know the answer, but I suspect it may come from a more enlightened attitude to gender in the coming decades or longer. Perhaps in time for the next London Olympics.