The idea that sexuality is dichotomous is crazy.
If you lined up all ~8 billion humans, and asked a heterosexual man to rank them in order of who he most desires sexually through to who he least desires, you would expect the most desirable end of the line to be populated with women who meet (or come close to) his ideal partners. But you wouldn't expect the least desirable woman to be ranked ahead of the most desirable man. (And I suspect that you wouldn't find the cutoff line beyond which he says 'I would rather not have sex at all than have sex with anyone below this level of desirability, under any circumstances' was in such a location as to exclude every man on the planet either). In that light, the label 'heterosexual' isn't really very meaningful. It's a tendency, not a certainty.
Really? You think so? I would say my “I won’t have sex with others” line does exist prior to the presence of women on the list. I completely comprehend other people having a different line, even a far different line. And indeed, the idea (the picture) of homosexuality does not make me squirm at all, let alone bother or worse. I just personally don’t have a flicker of interest.
Yes, I do. Not necessarily for every heterosexual; But for many. Indeed I suspect that that line of eight billion will include a large number whose gender you cannot be completely certain about while they have their clothes on; and that some of those people would fall ahead of the cut-off line for the vast majority of people. Particularly after an opportunity to converse and interact with them socially.
We also see this borne out in situations where men are separated from women - some men who are very definite that they are heterosexual before being isolated from women will form sexual relationships with men in those contexts.
Of course you could argue that they were not 'really' heterosexual beforehand; or that their relationships in male-only environments represent some kind of aberration. But that just rolls us back around to the idea that the dichotomy is meaningless - people are heterosexual until they aren't.
At the end of the day, we aren't attracted to genders; We are attracted to characteristics of individuals.
If you met a man, fell in love with him, and he then revealed that she had female genitals rather than male ones, would that undo the fact that you had initially considered her an attractive sexual partner?
It's ridiculous to imagine a heterosexual man in his twenties being more attracted to a nonagenarian woman, than to a transsexual man of his own age and preferred appearance, who he believed to be female.
The confusion, outrage, betrayal and even anger that one might feel at the 'deception' of discovering that your attraction to someone was homosexual, when you believed it to be heterosexual, shouldn't get in the way of recognising the fact that sex organs aren't even something we know about in most partners, until after the decision about whether they are sexually attractive has already been made.
Rendering the homosexual/heterosexual dichotomy meaningless. People are attracted to individuals, not genders.
Sexual preferences are usually presented as inclusive (I am attracted to women), but in fact they are exclusive (I am not attracted to people who look like men). This is made obvious if you consider the fact that the vast majority of people do NOT find every member of their 'preferred group' attractive. (I am not attracted to people who look like men. But I am also not attracted to cross-eyed women; Women who are underweight; Women over the age of 80; Homophobic women; Women under the age of 35; Women who pick their noses and eat it; Women who slurp their soup; etc. etc.).
The fact is that very few people find every single person of their preferred gender a turn-on.
Sexuality (for non-Bi or Pan individuals) is just the first of many exclusions that cut down humanity into a small subset that you want to have a sexual relationship with. It says what we are NOT; and very little about what we ARE.