I found this article to be so on point!
.... there is the threat posed by potentially being attracted to a trans woman. You don’t even need to actually be attracted to her, just the idea that you might be, or might be attracted to someone like her, can end up being similarly destabilizing and terrifying. Like gender, but perhaps not to the same extent, our sense of sexual orientation is another very important and very central facet of our identity. In so far as most cis people aren’t able to simply conceptualize a trans person as the presented gender and leave it at that, they end up taking the comforting consistencies and certainties of one’s sexual attractions and throwing those into chaos as well. A man might wonder if it “makes him gay” or could “turn him gay”. A straight woman might fear the same. A lesbian might fear becoming straight. And so forth. The fact that trans women, by virtue of being women, are culturally positioned as sexual objects makes this a bit more prominent. And when you throw in the conceptual emphasis placed on the sexual aspects of a trans woman’s body, the cultural sexualization of what transition is (it’s all about boobs and vaginas in the documentaries; they don’t much talk about skin, scent, body hair, fat redistribution, lasering away the facial hair, changes in fingernail strength, muscle loss or all that other random stuff… just the sexy sex-times parts), and the degree to which our conception of gender identity and gender expression is confused with sexuality, and even the kind of attempts to conceptualize her gender I described earlier can lead to contemplation of her sexuality.