Honestly, I think it goes deeper than that, I think that many guys that go for trans porn actually are very into it, probably because it's such a "taboo" subject for them.

It's similar to whenever there is a Republican or conservative convention somewhere, immediately it becomes a Grindr hotspot.

There are boat loads of gay / trans people in those extremist communities, because of course there are, and while publicly they will bash anything LGBT, privately they get off on it

See also that mega extremist church pastor that would constantly bash the gays and then got caught snorting coke from a gay prostitute

Edit:to add to this: I think that most trans porn made is not primarily made for trans people, but for men. Similarly to how most gangbang porn also isn't for girls, it's for men. Sure, trans people and girls can watch it, enjoy it, everyone is free to do whatever as long as they don't hurt anyone or thing, as far as I am concerned, but the main audience is just plain men.