I went on a weekend for an adventure sport.
The UK's governing body were holding it, to encourage more women into the sport.
They had found, through research, that a lot of women were put off trying the sport due to men and more generally due to coaching techniques not being suited and sympathetic to women.
The men took a macho attitude to the sport and were much more confident. This in part is due to their bigger size and strength. Stuff like considering equipment differences was also relevant to this.
The weekend rather than being a competitive enviroment with men showing off, was one of collaboration and mutual encouragement with the wide range of ability and skill sets.
The coaching was different. It took into account that women had less strength and needed to focus a lot more on skills and needed longer to become confident in what they were doing. They were less competitive and showing off wasn't a thing at all. There was less pressure to do things outside your comfort zone and instead within your own time frame, rather than someone even well meaningly going "come on, just get on with it" which really can be off putting. Its not at the level of "stop being a wimp/girl" but thats how it can feel at times. No one wanted to be the centre of attention or to be around others looking to be the centre of attention.
A transwoman present would have raised certain issues. Firstly shared accomodation for the weekend - lots of women went by themselves and shared with people they didn't know. Secondly, there would still be issues with male socialisation and attitudes - transition doesn't stop many elements of this. Thirdly there's the physical size and strength issue, which does affect confidence and frankly empathy levels. And lastly there were conversations relating to biology - how periods and menopause were affecting women and their experiences with sport.
The feedback the weekend got was, yes it was really helpful and helped women feel more able to participate WITH the men because it had given them a confidence boost they otherwise would not have had. It also gave the governing body and coaches the opportunity to reflect on how the sport naturally defaults to an enviroment that suits men rather than actually being gender neutral and you do need to treat men and women slightly differently due to physical strength, size and socialisation in order to be a unisex sport.
As a rule, I've always found it a particularly welcoming sport and the men really accepting of women despite all this. Theres a lot less sexism than some other sports. But it also was a huge relief NOT to have men there as it really took off pressure and there was more understanding of how its much more challenging for women in various ways. It centred the needs of women rather than the loudness of men.
Saying this shouldn't be allowed, because its on a par with racism really fundamentally is missing the point and tone deaf to how the world works in practice for women and how their life experience and biology impacts on their participation for simply everyday things.
The entire aim of the weekend was to STOP the self exclusion of women from men within the sport. Not to segregate indefinitely by sex. The weekend was a gateway to that. It was about levelling the playing field to increase equality. If you force women to accept males into that environment, you would immediately have some who would self exclude because they are intimidated or the atmosphere changes or puts some subjects off limits. Indeed it ends up reinforcing exclusion of women from participation.
Transwomen simply do not share in the same socialisation or the same physical limitations. They have other barriers to sport, but these are not going to be solved by going to a women's only event. They need their own unique pathway to solve their own specific problems.