One point I'd like to add is that trans identity can become an existential threat to a lot of people, in the philosophical sense of existentialism vs essentialism. If you base your entire life, identity and values off a single idea, then questioning that idea brings into question your entire existence. If you think your a man because you have a penis and that your hetero because your attracted to Afab women then the idea that a women can have a penis brings into question both of those identities and all the decisions in your life you made off those identities.

If you aren't secure in your sexual and gender identity these sort of questions can be very uncomfortable as doubt would lead to you doubting and regretting every decision you've made in your life leading to an existential crisis. So instead of facing this existential dread people will run from these questions and attack anything that may raise them to preserve their identity and ego.