I get that MIR, I do. I don't think this is some elaborate slow play for some bro to get his jollies. And no, what's downtown does not define who you are, but its not irrelevant either. But I don't think its unreasonable to expect that teenage girls can go to the bathroom and change clothes at school without a person with a penis present. This young person is not a martyr.
You've yet to articulate why having "a penis present" needs to be the prevailing factor here. Are units some kind of robotic lust monster, like 21st century sirens? I changed in sports locker rooms for every sports season for every year of middle school and high school and I had no idea what any of my former teammate's crank looked like, not sure why this has to be any different for girls. If I wanted to see what someone else's junk looked like I could have looked, I made a choice not to my life was unaffected. I'm sure I had a teammate or two who were more curious than I and had the urge to look, and I am sure they don't bear any scars from meat peeping. I don't know why girls can't be trusted to treat penises in the locker room any differently than boys do. Locker rooms are awkward for most people, I'm nearly 40 years old and I still am not comfortable in a locker room.
Look I acknowledge how this can be complicated for some, maybe even most people, but if one can't articulate what the issue is beyond, "but it's a penis," then there should be some further introspection as to what the issue is here. Can you honestly say you would have the same objection if this was a girl transitioning to a boy and wanted to change with his male teammates?