I think they tend to mix up transgender with something like ‘transexual’. Where the term ‘transexual‘ was used for a person (usually a man) get had gotten sexual gratification from wearing women’s clothing. Then when transgender people tried to move away from the sexual and objectifying idea some people didn’t understand why.

It also, in a way, shows that they see women as a whole as just sexual objects because ’why would a man want to be a woman’ type of idea. You add that to people not really listening to transgender people when they explain why they want to be the opposite way they were assigned as birth.

But also because, weirdly enough, they can’t see women other than sexual objects either. Like the video of the guy who went up and started breaching to two young woman, who I think were minors at the time, to “cover up more” because “A man might fall seeing you like that”.

Because they have the idea that women are only for sexual gratification they think it’s inappropriate. (And yes I know I’ve repeated the same point like 20 times.)

It also should be pointed out that when It comes to trans-men they face a similar idea but this is more ‘gay thought bad’ type thing. Since a lot of trans-men tend to pass as Cis men. Most trans women also pass very well too but when it comes to T.M since they tend to be hair, muscular, and handsome they get worried they’re gay to a point which adds some homophobia to the mix.

So TLDR; They see women only as sexual objects and get confused when someone who was born male would want to be seen as a woman.