Ok. Now, back to this.
What if a hot-blooded hetero cisman gets attracted to - and turned on by - a beautiful, confident woman at the next table to him in a restaurant? And then he overhears that his hormones have actually been stirred into action by...... a transwoman?!
Should he perhaps march over to her and demand an apology for making him feel so stupid and cheated in his now-wasted lust for her?
That would be stupid, and you know it, and there really is no meaningful connection.
I can't think this whole line of argument is going to end very well (logically-speaking) for you. But I'm sure you'll tell me how my example is
entirely unrelated in every way to what you're describing...
I wouldn't say "entirely" unrelated. I would say that there is just enough connection that it might be used to mislead people away from the obvious issue, which has no meaningful similarity to what you have described above.
(PS: If you want another counterexample to do the same treatment to.... how about a hetero cisman starting to date a ciswoman; they are both really into each other, and after several dates the man's thoughts turn to sex (intercourse) - something which to him is an extremely important component of any relationship - but it's at this point the woman tells him that because of serious complications from endometriosis, she's unable to have intercourse. Should our man feel cheated and slighted that this woman has - somehow, and in his eyes - misrepresented herself to him from the get-go?)
This one, on the other hand, is a bit closer.
First, as noted before, it is incredibly unlikely that it took several dates for the man's thoughts to turn to sexual intercourse. It probably happened before the first date, and certainly before the second, assuming the people involved are both young and single.
Now, exactly when, and how, the woman ought to reveal this issue is very complicated, and is influenced by culture, religion, their individual personalities, their other relationships, and a whole host of factors. However, in general, one partner, frequently the male, and in this case it was stipulated as the male, makes a certain amount of investment (of time, effort, money, something or some combination of somethings) in getting the woman to bed. At some point, it is very, very, obvious that that is exactly what the partner, in this case, the male, is doing. When it becomes obvious, yes, she ought to reveal this problem, and if she allows him to continue investing without revealing it, he really, really, ought to feel cheated.
In the case of the woman being a transwoman, that secret should be revealed very early on, really before any significant investment at all. Like thePrestige said, that would be a case where the woman isn't even in the eligible dating pool, and the guy really needs to know that, quickly.
The medical issue isn't a great analogy to the secret that the target of the man's affections is a transwoman. It's not bad, but it could be better. A better analogy, although still not perfect, would be a situation where the pursued female is hiding the fact that she is, despite all appearances, actually 14 years old. That's the kind of thing that needs to be out there on the table as early as it possibly can be.
ETA: Also, see Emily's Cat's response. It covers some aspects I didn't.
