I think this is a legitimate concern to not want males in female restrooms (and I have heard it from females, not just Carl). I think to address this concern it would be much better to only have a rule that prevents adult and teenage males from using female restrooms, than have a rule that requires everyone to use the gendered bathrooms. In otherwords, let anyone use the male restrooms, and only restrict female restrooms. Restricting use of male restrooms to people born male actually forces people who are dressing and acting like males (and depending on how the rule is defined, people who have male genitals) into female restrooms, which is counter to stated goal.