I get what you are trying to say.But I still can't compare that to basic sexual orientation and sexual preference.As long as a man believes a trans woman is really a male.Or heck even 'more male" than female ....he (a heterosexual cis male) will think he just found out he engaged in homosexual sex .Which goes against his very core sexual nature.
And please understand.I'm not "endorsing" .I'm not even saying its "right or wrong".Just what I believe is going on in the mans head.(many men's heads not all)
But what I mean is, you're not providing a clear reason to differentiate based on invisible race, or invisible chromosomes. Just saying something along the lines of "one is race, the other is gender identity" doesn't resolve the comparison. They're both things that did not impact his attraction during the casual sex experience, and do not necessarily impact the person's personality.
I think a clear difference between permanent instincts, and social taboos, are that social taboos can be quickly changed from generation to generation. Racism was/is a social taboo, and now homophobia is a social taboo where some people, especially younger people, have statistically less and less of a problem with it, while other people, especially older people, still statistically have major issues with it.
We can't really say that example person's racial issue with Asians is valid. At best we can say, "Well nobody is going to force you to have sex with anyone, but you might want to look into that..."
But some people are saying the person's homophobic issue is valid. That it's valid to be repulsed by something that he didn't previously notice, that didn't affect the night, that doesn't necessarily say anything about the person's personality, or anything like that. It's different than not being attracted to someone who is clearly you're own sex, because he was indeed attracted. Just because homophobia is more common than racism currently is (and probably comparable in frequency to what racism used to be like), I don't think that means it's more valid, than racism. Certainly not to the point where ethics have to be constructed around their issues about invisible things that they can not articulate and explain.
And like I said, it comes in layers:
Could the person in that example explain why they wouldn't ever have sex with a trans person?
Is it a legitimate issue about their appearance (for some trans people), about other senses (like someone maybe not wanting to have sex with a current smoker if the breathe bothers them), or about the surgical results between their legs (apparently it goes unnoticed by some)? Is it a misunderstanding of the causes of transgender status, thinking that it's a personality fault or that the person is perverted? Is it a concern about harm (like someone's married, or someone has an STD, or the risks of producing a child from incest)? Or, can a person like someone's appearance, have no issues with a person's personality, but still find themselves repulsed by the idea of having sex, without calling it an irrational fear or disproportionate reaction? And what if they already had sex with a trans person without knowing and enjoyed it? What does that say about the later assessment of their repulsion towards it?
That's why I think, and others seem to think, there are multiple layers here.
-There are regular preferences, whether they make sense or not.
-Then there are strong repulsions, phobias, where the problem cannot be articulated and yet hasn't affected the actual act of sex or the person's personality. But even then, there's a polite way to handle it, a way of taking responsibility for one's own disproportionate issues.
-Then there are people with strong repulsions, that then blame the other partner, or expect society to revolve around their repulsions, rather than to take the responsibility to make sure their own repulsions are not present. That would be Tom in this case.
Tom wouldn't get much heat if he stopped at step 2. People might say, "well that doesn't seem to make any sense, it seems to be a social taboo or phobia to be freaked out in hindsight about non-harmful invisible information", but if he's not expecting other people to validate and revolve their ethics around his issue, then it's not a giant deal.