This happens to me a good deal in womens’ bathrooms, because of the very opposite— I have short hair. Additionally, I don’t dress in very feminine clothes. Most of the time it’s okay, but the few times that people are outright hostile does make for an upsetting experience. While we sometimes laugh about it (you’ve got to cope somehow, and some of the experiences are genuinely amusing), it’s always saddening to hear that it happens on a larger scale.
Well done to your son for taking it in stride, and for not letting it sway his confidence or self-awareness. And thank you for writing about it!