"Should trans women be allowed to compete in women's sports" I don't think there should be women's sports. I think it's a silly artificial construction that only upholds the gender binary while it's benefits are incidental and would be better addressed directly.
Care about giving people with different body types and muscle mass a shot? Split your league by weight categories like boxing, or some other direct physical measurement. Gender is at best a poor proxy for these and we only do it because we still treat women are a different species. "But that still wouldn't be fully fair to everyone?" Sport isn't fully fair, it's about rewarding people with the most biological advantage. That's the whole point of it.
You want to give more sporting opportunity to women and minorities specifically? Okay then do that. Create your own opportunities league, but if we're giving up the pretense that it's about essential biological advantage then you better let trans women in.
What's that, the extra league would be treated as a novelty afterthought and would lack the prestige of the real main event? You mean like how women's events were treated when they were introduced? True! In fact women's leagues are still largely treated as secondary now, and you know how we can fix it? Make the main leagues open to everyone with weight, height or muscle mass categories so that people with different body types can excel. Like I suggested before. Problem solved.
Women's sport is bad actually.
