Would you feel differently about a post-op trans woman? I assume the hang-up is the penis on a woman?
Do you think a penis would be a deal-breaker even if it were feminine: soft, flaccid, more like an oversized clit than a penis? Would it change anything to know lots of trans women's penises don't ejaculate, but instead produce wetness like a cis woman would when aroused?
I don't doubt the gential preference, I just sometimes think straight men think of the female penis as being like a man's penis, and that's not usually the case.