Bit of a switcheroo but go point out all the ways that these trans exclusionary rules also hurt cis women. Top female athletes in a variety of sports, like Caster Semeya have been banned from their sport due to natural differences in their hormone production.

Under these regulations, promulgated by the sports governing body regulating track and field, women like Semenya, who have naturally occurring higher testosterone levels associated with Differences of Sex Development (DSD), are barred from competing – unless they subject themselves to medically unnecessary interventions to reduce their testosterone levels and conform to an arbitrary and subjective standard of femininity. These regulations came into effect in 2019. Sports governing bodies argued that the regulations broke from the past 50 years of sex testing women athletes, a practice that was humiliating, degrading and discriminatory. However, the revised regulations still subject women athletes to sex eligibility criteria that retain these negative, rights-abusing consequences.

These practices are degrading and discriminatory and undignified.

TERFs will also actively attack and question cis gendered female athletes who have short hair, thinking they are trans.

These acts of discrimination hurt trans men and women, or attempts to exclude them, but it also ends up hurting cis gendered athletes (basically arguing for solidarity here). Every time these bills or exclusionary policies are passed, trans and cisgendered women that do not fit the concept of "normal" looking female are actively harmed. The Bathroom bans in SC, led to lesbian masc women being harrassed by cops (MEN!) inside of bathrooms and having their autonomy violated for going to the restroom. The very thing they were allegedly trying to "prevent".

We also have a human right to free association and human dignity. Why should women (cis and trans) be forced into genital checks or sex testing?

I might also add that sports are treated as an avenue to "rise" in their class position. With kids often cultivating specific athletic careers not just for fun, but because their parents want them to get full/partial rides to college, and possibly make it to the Olympics. If Athletic activities were not high-stakes, with so much riding on the individual performance of specific athletes, the pressure to exclude athletes with alleged "advantages" would cut off. It ultimately comes down to capitalism. Make college cheap, or free. Abolish university sports other than inter-mural leagues. And invest in more accurate research on the effects of estrogen / testosterone on transgender people and sports performance. I know there's papers on the effects of estrogen on muscle density and bone mass. Even if a man was actively trying to switch genders to have an advantage against women, aren't they handicapping themselves? To go through the gender dysphoria, possible mental issues of hormone imbalance, a man could just...train and git gud, or quit.

If it is about "men" in female locker rooms, or predatory creeps interacting with cisgendered women. It should be noted that there's already enough cisgendered creeps actively violating women in women's sports! Without any need to pretend or switch genders. They are called COACHES and DOCTORS. Point them to the The largest sex abuse scandal starting in 1990s, zero trans predators. The FBI even declined to pursue early reports:

Coaches and officials perpetrated, facilitated, or worked to conceal abuse in Michigan, Pennsylvania, California, Rhode Island, Indiana, and elsewhere.[8] FBI agents declined to investigate early allegations of abuse, then lied about it, according to a U.S. Justice Department report. Leaders of USAG, MSU, and the United States Olympic Committee (USOC, later USOPC) ultimately resigned; several coaches and officials faced criminal charges.

A central figure was Larry Nassar, a national-team doctor for USAG and osteopathic physician in MSU's athletic department. More than 265 women said Nassar had sexually abused them under the pretense of providing medical treatment,[9] including former USAG national team members Jessica Howard, Jamie Dantzscher, Morgan White, Jeanette Antolin, McKayla Maroney, Aly Raisman, Maggie Nichols, Gabby Douglas, Simone Biles, Jordyn Wieber, Sabrina Vega, Ashton Locklear, Kyla Ross, Madison Kocian, Amanda Jetter, Tasha Schwikert, Mattie Larson, Bailie Key, Kennedy Baker, Alyssa Baumann, and Terin Humphrey. In 2017 and 2018, Nassar pleaded guilty to federal charges of child pornography and state charges of first-degree sexual assault; he received sentences of 60 years in prison plus another 80 to 300 years.