This is a serious question

Why do some men and women freak out when they find out someone they were attracted to turns out to be transgender or intersex. For example, some straight men will freak out if they find out a very feminine looking woman with female secondary sex characteristics is biologically intersex or male and then say nope there aren’t attractive when they just said they were. Same thing with some straight women, they see a handsome looking man who turns out to be intersex or transgender and then say after they aren’t attractive when before finding out indicated otherwise. They don’t have to date, marry, or sleep with intersex or transgender individuals if that’s not their thing. I cringe a little bit because then their sexuality is in crisis. So straight men are naturally attracted to feminine sex traits and physiology while straight women are attracted to masculine sex traits and physiology and I’m just wondering why they worry they must not be straight anymore? To be honest in some cultures with heterogender relationships only the intersex or transsexual individual would be considered gay or homosexual while their partners wouldn’t. For example the HSTS ladyboys in Asia make pretty women even though they are not biologically female. And the strange thing their penises are not really used for anything there are just there. I think sexuality and sex and gender are more complicated than most people think and there is so much gray area. Why is their heterosexuality threatened?