As my friend states in the video, she does not use women's toilets; she uses disabled toilets because she's disabled. I have never seen a transwoman (at least not one that doesn't pass!) in a women's toilet. I also suspect it is still far more common for women to be assaulted by men that identify as men. Additionally, transwomen on estrogen (I imagine most transwomen) will likely find it difficult-impossible to get and maintain an erection because it blocks or cancels out testosterone so is effectively chemical castration.
But where would he go if he were not disabled? Just because he isn't using women's loos doesn't mean other big burly, possibly weird and predatory men in dresses are not. There is a man in my town who obviously has some mental disability or mental illness, who walks around all day with a variety of different dresses over the top of his otherwise completely male clothing. His hair is long but no make-up, no heels. He doesn't pass in any way whatsoever and it doesn't seem that he even tried to. He's a BIG man and clearly mentally unstable to some degree or other. He is very strange and quite intimidating looking, always has a very intense scowl on his face. If you'd found out he was a flasher or a high school shooter you'd say 'yeah, that figures.' Possibly harmless, possibly not, but there is absolutely no way any woman would feel comfortable meeting him head on in a ladies' bathroom, or anywhere when she was alone.
Just because you know a trans identified person you believe is harmless does absolutely nothing to prove that they all are. And we know very well that some of them ARE a danger to women. We know it. It's not hunch, it's a proveable fact.
What you are doing is the same as saying it's perfectly okay to ignore signs on entering fields full of baby lambs, or beaches full of basking seals, saying 'please keep your dogs on a lead'. Your logic is that because no lambs or seals are going to be have their throats ripped out by a bichon frise, it's okay to let breeds with high prey drives or strong hunting or fighting instincts loose, because they are 'just dogs who mean no harm and can't do any real damage' too.
The sooner people like your friend realise that women wanting to protect themselves, their daughters and other women isn't some baseless or bigoted personal vendetta against them personally, the better for all of us it will be.