I don’t think she is saying that anyone has an obligation to sleep with anyone. I think she is just saying that if someone says they sleep only with men, but then says they could not see themselves with ANY trans men, then what they are saying is that they don’t see trans men as men. That is transphobic. Likewise, if someone says they don’t see trans women as women. If someone said to you, “go away, I only date women,” (or worse, “I don’t date men,”), would you say that’s OK? It’s not about whether they want to date you in particular. It’s not even about anatomy: I once dated someone who determined after we dated a short while that she couldn’t be with someone with a penis due to past trauma. I totally understood, no hard feelings. I don’t think anyone would find that transphobic. In fact, I would have understood if she had said that when we first met online and I had pointed out that I had my pre-op trans status included prominently in my profile, but she had wanted to try anyway. Anyway, I, too, don’t want to date anyone who isn’t attracted to me, but I don’t think that’s what the author is saying.