Do you find biological or genetic advantages in sports unfair in principle? If not, then what's the difference in this specific situation?
The level of difference of course.
That's why men and women don't compete in the same events as otherwise there would be no elite female athletes. 15 year old schoolboys are better than elite females in most physically demanding sports.
Nothing factor is more closely connected to performance than being born male.
Are we back to the anti-trans bedrock argument "trans women aren't real women"?
How transwomen should be viewed socially as a matter of courtesy and respect is different from should they be allowed to compete in specific sporting events.
Where do you draw the line for sport?
Is simply self-identifying as a women sufficient to enable one to complete in women's sports, or is there some threshold one must cross?
If the former, elite women's sport will no longer exist as grifters will just go for the prize money. If the latter, you have the same problem of saying some transwomen 'aren't real women' as they haven't met the threshold so shouldn't be allowed to compete in the sports.