OK, a mental illness then. But that is complicated by the fact that you cannot expect a mentally ill person to take responsibility for his actions.

Hey wait, ora... I reject your implication that any man who would rather not be with a trans woman is a bigot. I fully respect the rights and equality of trans people everywhere to pursue happiness, and I do this while maintaining that they must respect my preference to be with only those who were born female.

This does not make me a bigot. I will again say that the responsibility for disclosure lies with the trans person, for the following reasons:

1: It is unreasonable to ask every hetero man to ask a potential partner if she was born a woman. This will anger/insult a lot of hetero females, I'm not justifying that, but you can't deny the reality of it.

2: It is not unreasonable to assume that a hetero man will be surprised and angry if he finds out that the woman he just had sex with was born a man

3: Even if hetero men DID ask every woman, would that then make the rejection or "cultural frustration" the transsexual feels when the disclosure is forced upon them any less potent? No, their feelings will be hurt just as much. It would be just as constant a reminder that society feels that they are "not real women" as if they themselves disclosed. An attempt to put the onus on the heterosexual is, in my opinion, an attempt to validate lying by omission.