Thank you for taking the time to write that. I read the whole thing and it is certainly thought provoking. I guess you could say I'm sitting on the fence with my legs on the "disbelief" side.
I have heard compelling arguments that a large number of post-op transsexuals have declining mental health after surgery, but it's hard to find compelling evidence in either direction. Of course, I also don't have the time or educational background to read through research papers (or the money, apparently, since for some reason scientific research is proprietary).
While I appreciate the educational background and practical expertise of the people you mentioned, I think too that if scientific research is indeed affected by political bias (and I've read from a few self identifying scientists that this is the case) then it stands to reason that studies done would be designed to support the political bias and avoid contradicting it.
One guy that comes to mind describing the bias involved in getting grant money for research is Thunderfoot on YouTube, who could be described as a critic of Feminism and Creationism and other pseudoscience junk, among other things (including scientist, if you ask me). Oh, look, there's a short Wikipedia article on him now. I'm not sure if I could find reference to him saying that on the spot if I tried. Though I'm reasonably confident that I've heard him say it, though I'm not sure in his general field of study of chemistry the bias would necessary relate to sex in any way.
According to his channel, he allegedly had one Feminist try to get him fired (I believe he reported that she ended up getting fired instead), and had his Twitter account temporarily banned because of alleged exchanges with the professional victim club headed by Anita Sarkeesian. That said, if you watch his videos, he is actually very intellectual and professional about it (while also having his fun). He's a favorite vlogger of mine.
If I'm not mistaken, I believe that Christina Hoff Sommers has also mentioned this, but again I lack references (so maybe I'm just putting words in her mouth). I guess she also doesn't qualify as a scientist. Only an academic.
That's not different than denying anything else that's pretty well scientifically accepted. Essentially all prominent organizations across the world that deal with the medical treatment and scientific study of transgender people agree that absolutely it is real and there's no way to deal with it other than to let that person be themselves and transition as they see fit, whether that be medically with hormones or socially in their presentation.
Science isn't really about what people agree upon. At one point scientists agreed the Earth was flat. Science is about what appropriately run experiments tell us about the world. Studying human brains is a bit more of a black box though. As far as I know, we've barely scratched the surface of really understanding it, and most of what we think we know is observational or self-reported.
Some medical or mental health professionals examined or questioned various people at various stages of their development or transition and came to some conclusions based upon that. I think it's difficult to compare that sort of science with say physics or chemistry where the experiment is controlled and you can say with certainty what the outcome will be.
So, on the topic of bathroom choice. Why does it bother you? There's little to no cases of a trans person ever sexually assaulting, "peeping", or anything else out of the ordinary. Ever.
I don't think that proves anything, assuming it's correct. One could reason cases would be rare because transsexuals are a small proportion of the population, and also instances of peeping might be exceptionally rare if they are hiding their identity or uncomfortable with their bodies, etc. Logically it would seem to indicate that if one was going to peep it should be towards the gender they're attracted to, which might very well be the gender they were assigned biologically. In any case, it's a difficult subject.
It's unfortunate, but I think that most of us would be more concerned about a transwoman in the female's washroom than a transman in the male's washroom... Similarly, we would be less concerned with a female in the male's washroom than visa-versa, even though females are also guilty of committing sexual abuses in similar numbers to males.
The transgendered people aside, there's also the argument that how can we police it if you let people choose. And should a trans person qualify to choose on the spot where they want to go? How do you stop a heterosexual boy from going into the girl's washroom? Could he just claim to be transsexual and get a free pass? I think that it's not so clear cut, even assuming it's a healthy and safe option for transexuals.
Yet, about 70% transgender people experience harassment and assault quite regularly. Within the last few years, the murder rates of trans women has been skyrocketing; go ahead and check the FBI's statistics on that.
I think violence is terrible regardless of who it is inflicted upon. That said, I also think that most people experience some form of harassment and assault somewhat regularly so it's somewhat of a misleading observation. I could certainly see how some minorities may experience more severe forms of harassment or assault. In that case, I think that further acceptance of differences in people is good and will hopefully help to reduce the suffering. On the other hand, I strongly oppose things like "safe spaces", censorship, and bullying of people that have differing views. That's not the answer either. People need to be allowed to arrive at acceptance on their own. They can't be bullied into it. That will probably only slow the process down.