Lesbians like me joined forces with conservatives. Now they're turning on us.
(www.queermajority.com)
People only ever propose co-ed sports when trans people are brought up. It's a thought-terminating cliche and a reliable indicator that the speaker hasn't seriously considered why sports are gendered in the first place.
Real ally: Trans women are women. They belong in women's sports because there is zero scientific evidence of trans women having any advantage over cis female athletes. Fears that they have an advantage are just bigoted gut-level stereotypes assuming that trans women are biological men.
Performative ally: Let's move to co-ed sports!