There's this rising narrative going around that if you ask specifically for a CIS partner, you're a transphobe. That could be true for some people but it's not fundamentally related to bigotry. Moreover, this narrative, the "if you only want a CIS mate then that is prejudice" is trampling on one of the most important rights a person can have: the right to choose who they want to get intimate with.
First of all, transmen are in fact men and transwomen are in fact women. Let's get that out of the way. This isn't a foot in the door for "trans this really isn't that" narratives. What this is about it is the freedom to choose who you want to be intimate with. That right is sancrosanct, it is absolutely inviolable.
And yes, there's plenty of issues that make transgender dating a special issue. If someone reveals their TG status they can be open to hate crimes and even deadly violence. However all marginalized groups are special in their own way. As a black man I don't think it's racist if a woman says she doesn't want to date a black man. I face oppression, too. My class is special in its own way. One group isn't more special than the other. None of us have the right to force ourselves upon those who don't want to be intimate with us, even by omitting who we really are.
Really, if you have to deceive or hide who you are in order to date someone, do you really want to date them? I wouldn't. That's not fair to you and you're denying them their right to choose who they want. What do you think will happen when the person wants a CIS mate and they discover the truth? They're going to get pissed and dump you. Now you have to shame them into staying with you: "If you loved me for real this wouldn't bother you"... that's not going to convince anyone. They're either going to leave, or they'll resent you forever. That's just how it is. You can be mad at that but that's about as effective as protesting the rising of the sun. There's just no way to win once you've gone down that road.
"I want a CIS mate" is not the same as "trans women are not women" - one is a preference, the other is harmful prejudice. On the flip side CIS people who do date trans people shouldn't be shamed for their choices either. A man should be free to date a trans woman and not catch flak about it. Trans people should be able to be openly trans and not face hate speech or threats to their well-being. This, without any exception whatsoever.
The fundamental fact is when you shame or worse abrogate people's right to choose who they want to get intimate with, it's not going to end well for you. All you're going to get is people who resent being coerced or bullied to date people they don't want to. And that's not something the country, or the world, will ever put up with. Except that right now, most people don't imagine they can be labeled a transphobe just for wanting a CIS mate. And unpopular opinion: that should be nipped in the bud.
I don't disagree with any of the content of what you said, but I've never met a trans person who defaulted to nondisclosure. And doing that is a very unsafe move for any trans person.
There is the typical "I'm gonna at least see if there's some genuine interest here before I decide if it's worth it to have this conversation," but I've never met anyone who would forgo that up to and after sex. I don't think this is common at all.
What is common is the stupid meme joke of "I went to fuck this chick and when she took off her clothes she had a DICK". It doesn't matter if it actually happens or not, cis people are often obsessed with being scared by the thought and it's just pathetic honestly.
Nevermind that yes, given how close minded most cis people are, doing this would be as you say a very unsafe thing to do (both physically and emotionally) or that it doesn't really make sense to just hope that a random cis person isn't going to react negatively (especially because cis people just can't stop telling and re-telling this kind of insecurity disguised as a joke). Also if you are having sex with someone you know so little about that this comes as a surprise to you... I kind of feel like maybe you shouldn't be complaining about being surprised by details of a partner when you didn't bother to find out anything important about them at all before you decided to have sex with them?? Sure having a penis or not doesn't really define who you are in any meaningful sense (that isn't imposed by society) but if you get to the point that you are going to be intimate with someone I just really am having a hard time fathoming why this wouldn't have already come up?
Ok maybe the trans person really has fallen for you and is in denial about how close minded you are... but even in that case (which feels more like a hypothetical than an actual common scenario) acting like this is some nefarious or mean act is ridiculous. The cis person just has to see a dick for a brief second, it is no different than going to the gym locker room for fucks sake, for the trans person now they have to deal with the emotional intensity of being instantaneously and aggressively rejected by a partner they thought was in to them and unfortunately might physically be in danger from violence now. How does this make any sense at all? It is a waste of breathe to talk about this shit all it does is force the spotlight on feeling bad for how fragile cis men's identities are given their insecurities while ignoring the very real physical and emotional violence enacted upon trans and queer people every single moment upon this earth.
The only other lame insecurity that disguises itself as a joke among cis people that can give this one a run for its money is cis-men's fear of their own butt and what might happen if they realized it felt good to have something up there.