No, I don't think I could. That is just my personal hang up though, as I would find it a bit to jarring to be attracted to a trans person once I knew. Not that I'd have to worry about it, since people have standards, and I am probably below those standards. I have no qualms against people simply for being trans though.
What I don't like the idea that people should have to change sex in order to act a certain way, since bodies are pretty much just shells when it comes down to it, and I see little difference in what can be accomplished by a male versus what can be accomplished by a female other than certain bodily functions (although science will someday probably enable a complete and utter perfect sex change), so when someone says they wish they were female, because they want to be more feminine or vice-versa, I don't think of them as needing to change sex, I think of it as society's strict enforcement of gender roles as keeping them from being what they are already capable of being with their birth sex.
I don't really know much about it though as I have never experienced the desire/necessity to be another gender, so for all I know, maybe people really do just desire to have their parts changed, and have no intention of acting feminine, they just feel that they should have been born with different hormones and genitals. Shows how much I know. I'll be in the Dunce corner if you need me.