The argument from Democrats is often "Well, it's only a very small number of athletes." This is true, but it doesn't make the situation any less unfair for the female athletes. Every biological male that makes a starting lineup is pushing a female to the bench. Every male that finishes first, second, third, etc is keeping a female from finishing in one of those spots. Every male that goes to the state finals or a postseason tournament is taking the spot of what should have been a female in that position.
Even in low numbers, it is simply not fair. People recognize that and push back against it, rightfully so.
There's a reason that males and females are separated into different sports after a certain age.
Follow the science, right?