from five zillion pages ago but
Let's pretend Hagrid identifies as a female.
Even though he is clearly a man he identifies as a female and what LGBT is fighting for is the right to be who you are based on what you identify as even though you look nothing like it on the outside.
Would you let this man go into the woman restroom? He is mentally a female so by definition he is a female according to the LGBT, so he now has the right to go into the women restroom.
Alright, point taken. What if we turned the tables, though?
Let's say Hagrid was actually born as a female. All growing up, he's felt like he'd be a male though - so he underwent hormone therapy and vocal training in order to make him seem more masculine. In the end, he has grown a beard, his breasts have long gone, he has a wide shoulder frame and talks in a gruff voice - with all his clothes on, it's impossible to tell that he's actually the female love.
Are you suggesting that this person be forced to use the female bathroom because of his genitals?