We have always had trans people; whether by that name or social role. They have been a source of awe, fascination or fear. Held apart, lauded and sometimes hated. Whether the 'third gender' or the shaman: invested with powers, their insights sometimes sought but frequently suppressed.
Even for those of us who "pass" as our gender and identify with it, it may not be enough for those who would seek to police your behaviour.
For who amongst us hasn't let their guard down for a moment to experience the disapproval of the group, revealing something - in word or deed - that you felt should remain hidden, but was so much a part of you? Summon that memory and for a moment you can share these girls' experience. The difference is that most of us can conceal those differences when we need to: imagine if by definition, that you couldn't.
The world must change for trans people and it is not unreasonable or impossible to expect it. We have nothing to lose and everything to gain from acknowledging what has always been there. We are evolved to be highly social creatures and our differences within that context make us, as a group, more astute and successful. In the long-run, people with unexamined motives are easier to outwit. The group that does not evolve is destined to stagnate.
Acknowledging that gender does not constitute the same baseline reality for everyone opens up a world of personal insight into your own condition as an individual. You can learn a lot about yourself from people who, on the face of it, are not like you.
But if you care to look a little longer they are a part of you, and you a part of them.