Some people need a very structured, simple, well-defined worldview in order to function. Sort of like a computer has to follow a set program or it bluescreens.

‘This person coming towards me is a man. I can tell by his bowler hat and dapper suit. Therefore the correct action is to say ‘good morning sir, nice weather today’.’ And ‘This person coming towards me is a woman. I can tell by her dress and long hair and makeup. She is married based on the ring I see. Therefore the correct action is to say ‘good morning, ma’am, nice weather today’.’

And so on.

A person not presenting clearly as either gender, or isn’t the gender they’re expecting, means the ‘script’ no longer works. They no longer feel sure of what to do, and that lack of control of the situation makes them panicked.

Really, a lot of this, and conservatism in general, comes down to simple structure and control, so these people feel they always know what to do and where they stand.

Because our society is a social contract, and to act wrongly means you get ostracized from society. In ancient times that was practically a death sentence, and I don’t think these folks have ever gotten over that. They fear becoming the ‘outsiders’, left to the wolves and lions.