I have this tendency to look at what is happening and the implications of acting like that more than the why. That leaves me with this black box of incomprehensible emotional mush. I feel like it tracks that every time they rag against blue hair, 15 seconds later they're gonna say some "and now you don't even know what gender your car is!!" They'd have some idea to the effect of this actress being more correct and therefore more beautiful. If you're confused, you should simply strive to be like her or (let's be real, they'd like "and" instead) die trying.
Do you really think the reason boils down to pure transphobia? Not like in conjunction with some loss of a privileged position where people couldn't talk back to you?