First of all, Sarah, I just want to tell you that you are one of the people here that I absolutely respect without equivocation, and I appreciate so much the thoughtful, often brilliant, things you say here. You are a gift.
Now, I have thought about this for a bit and I am going to give you all my actual thoughts on this business of obligations. I know it will be too much of a soapbox for some, and I am sorry (kind of,) but I have to say this.
Saying it is morally wrong to not disclose is loaded with some pretty terrible subtext. Implicity it says that trans people are gross, that the feelings of transphobes and homophobes (these are the people that would be disgusted by the idea of "being tricked" by a trans person, right?) are more important to protect than our own feelings. I guess because we agree that we are disgusting? I would never disclose to a potential partner out of concern or in consideration of the terrible people out there who hold horrible, destructive worldviews. Never. I would do so only for my own internal reasons, or in consideration of the bond being created with somebody I like a lot.
I will freely admit that the social contract (which is written by the heteronormative majority btw) probably does currently state that trans people should always disclose their status no matter what. However, when the social contract is unjust, the persecuted and their allies have an obligation to stand against it, in my opinion. I hate to take an argument in this direction, but I'm gonna... 50 years ago there were people that were disturbed by the idea of using a toilet after a person of color, among other horrible things. The social contract of that time basically agreed with them, even enacted laws that supported that way of thinking. The people being told they were worthless and lesser at that time created a whole movement against it and things changed.
Maybe we need to stand up against what society tells us, especially when it is so demeaning. We probably never will tho, because we can't agree on much of anything and can't even get along with each other half the time. We take all these distict groups and we try to put them under an umbrella and pretend we are all the same in the name of solidarity and for the power in numbers (even though consolidated we are still a super minority.) It is a great and noble idea. However, we want to pretend there aren't lines drawn between us underneath the umbrella, but the reality is we are disparate and have often competing agendas. With the dynamics that actaully exist, any hope of all of us presenting a united front almost seems naive, especially to people that have been watching this for a while.
I personally do like the idea of coming together, and even totally support coalescing with the power held by the LGB community in hopes that maybe we can get some rights so that maybe one day we won't be so marginalized. But then I see people within this community turn on each other, time and time again, and I wonder how can we even believe in it anymore honestly?