I'm trans and I'd be fine with it and I think of the arguments that it's transphobic as misguided at best, malicious at worst. There seems to be a vocal contigent of transwomen who identify as lesbians who try to argue that a lesbian who is not trans and doesn't want to have sex with a transwoman (even one with male genitalia) is transphobic. This sounds to me like a kind of very, very bad pickup line.
On the other hand, I'd like to know what the OP, shtps, would think if they dated a transwoman without knowing she was trans and later found out about it. People have committed violent crimes because they didn't know, or at least claimed they didn't know as a defense.
So there is something there that needs clearing up. If you're attracted to someone and then later find something about them and decide you're not attracted to them after all, that's not the fault of the person you initially found atttractive. Agreed?