Without reading a full report, let me guess what happened here. Several boys go into the bathroom, and this girl is either in there, or comes in later. The girl makes some show of being there (maybe even said something aggressive: “What are you looking at?”). The boys get angry and tell her to leave, or that she shouldn’t be there. More argument. Then one of the boys says something like, “So, you’ve got the equipment to be in here? Let’s see!” Then you get the assault.
The boys are obviously wrong. Just like mugger who robs a mark in a dark alley. And just like a mark that walks home counting hundred dollar bills through a dark alley, this outcome was completely foreseeable. Not right. But foreseeable.
This is what society has come to...
The thing is, if the girl/ "boy" went into the girl's restroom and started acting like, well, a teenage boy and leered at, or "came on" to the other girls, I'd wager that the girls would have also been pretty mean and may have assaulted her/him. Sure the assault is wrong and terrible. No argument there.
IMHO, since "transgendered" makes up a tiny fraction of an already tiny fraction of gay/lesbian members of the general population, why not just simply have at least a couple of "unisex" bathrooms?
Once they've locked the door, totally privacy to be whatever they want to be.
Poop in peace.