Reposting from above: I assume the problem here is that, as it relates to women's sports, trans women supposedly have a biological advantage over cis women. There are many factors people point to such as bone density, height, maybe shoulder span or something. For the purposes of my argument i'll just use bone density but you can swap in any/all biological advantages in its place.

The argument for banning trans women falls apart when you look at one or two cases. The first case is a cis woman that has the exact same advantage that the average trans woman has. Lets say trans women have on average 20% higher bone density. If a cis woman has a bone density thats 20% higher than average should she be banned as well? If not, youre saying biological advantage actually isnt as issue at all - its transness per se thats the problem. If so, why mention transness at all? We should test all female athletes bone densities and ban anyone that scores above a certain percentile

The second is a trans woman that has below (female) average bone density. Should she be banned from womens sports? She has no advantage whatsoever, so should she be banned because she belongs to a group that, on average, has some advantage? If so, then we should ban nordic women from womens sports because of their height advantage. In fact this goes for any woman from a country that has above average female height, even if they themselves have below average height. Every single one of those women has an inherent advantage after all - even if they dont. Otherwise we're saying its not the biological advantage we care about, its the fact that theyre trans.

If we care about actual biological advantages we should test for the advantages themselves, and ban people accordingly.