It's all good, I'm not getting mad, I appreciate the dialogue too.
It's nice to have a conversation on the internet where it feels like both sides are really listening, that can be rare!
Your analogy makes much more sense now that I understand you were talking about it from the perspective of the woman dating the married man, not the wife. I still think it's a very different scenario though. In the married man scenario, there is a third party (the wife) whose life is being affected by the dating, it's an unethical situation (cheating), and it's part of what's happening in the present (whereas for many trans women, their transition to female is in their past, it already happened).
Why couldn't the man just wait until he was divorced to start dating, thus acting in an ethical way and not involving the woman he's dating in cheating? He's making a choice, he doesn't have to be a cheater. Whereas a trans woman who's dating is not affecting any third parties, is not doing anything unethical by being trans, does not have the choice to be trans or not (born that way), and it may well be part of her past. I just don't see it as immediate, vital information in the same way, for all those reasons.
And yes, I am MUCH more worried about the trans woman in this situation. The guy she's dating might suffer some embarrassment if his friends or family are prejudiced, ok, I get what you're saying that that might suck for him. But if we're supposed to love and accept ourselves, shouldn't he love and accept himself as a man who can be attracted to women both cis (born with sexual organs that match their gender) and trans (born with mismatched sexual organs)? The worst case scenario there seems to me to be that he learns something new about himself, and has to deal with some teasing or judgments from other people in his life (and if they do judge him harshly, they're being really terrible).
On the other hand, the trans woman could be fired, she could lose her apartment, she could get beaten up or killed. You hear about these sorts of things happening to trans women on the news all the time. Anything remotely like that is very, very unlikely to happen to the man in this scenario. The woman is the vulnerable one here. So yes, I'm much more worried about her.
All that said, what you're saying IS helping me understand how much of a shock it could be for a guy in that situation and how he might feel very weird about it. It's easy to forget that sort of thing, since I'm bi, so it wouldn't matter to me, and since I have a roommate who's trans, so I've given these issues lots of thought over the years.
As for when to disclose things, I wouldn't consider it to be wrong for someone to wait until a second date to tell me they'd been married before, or had been to prison for a non-violent crime, etc. That's just me though, people may have different opinions on when you have to tell your life story in order to be honest with someone you're beginning to build a relationship with.