A biology teacher going by the name Grace Ann on Facebook shot down the idea of transphobia as simple science in a now-viral post. She wrote that she saw a post along the lines of "females have two X chromosomes, males have an X and a Y, it's not that I'm a bigot, it's just that science says it has to be this way."
Well, that didn't sit right with Grace Ann (being an actual science teacher and all), so she responded to that post, and then posted the response on her own page. Basically, she shoved the whole idea of chromosomes dictating gender into the trash can, where it belongs.
First the science teacher brought up a bunch of species that don't even have X and Y chromosomes (birds, for example, are ZW and ZZ) and some that develop into one sex or the other based solely on environmental conditions (lizards). Then she got to humans, and pointed out a number of cases wherein males and females don't simply have XX or XY chromosomes.
There goes your science, buddy—turns out, nope, you're just a bigot. Try learning some stuff, that might do you some good, random transphobic person, whoever you are.