Here's a video I saw some time ago, but it won't be obsolete anytime soon, if ever (though we can hope). The United Nations. There is a very nice introduction, but the actual speaker starts about 3:15 in. She...well, she gives an amazing, passionate and succinct defense of rights for transgender people. And says why we shouldn't be wed to our own ideas of how sex and/or gender should work. Really, the lesson she teaches here is deep rather than broad, and hopefully it sticks.