But to clarify, I don’t think anyone is born in the wrong body but I do think that some people seem to believe this so vehemently that they are willing to mutilate their own bodies for it and live in a way that makes them a target for hostility.
I think there are two things going on here with this "hostility".
I don't think people who identify as trans should be persecuted or harmed, or told they can't wear what they want etc. (within the same rules of decency that apply to everyone else.) There is such a thing as actual transphobia/hatred and persecution of trans people which I don't condone at all.
However, pretending to be something you are not, and demanding that other people agree with you or be forced to pretend they do, is going to piss people off. It's human nature (for good reasons) to object to forced speech, lies and fakery. Society is built on a manageable level of mutual trust and the ability to call out deceit, danger and untruth. As a whole, world society says no to people pretending to be something they're not, because if we didn't things would fall apart, and how they feel about it doesn't really come into it - as with Rachel Dolezal, the guy who wanted to identify as a different age etc.
That is why IMO this modern trans phenomenon os causing so many problems and arguments. Not because people aren't generally tolerant of differences – they are. But because it's actually normal and reasonable to not like being lied to and forced to lie, and to feel uncomfortable about deceit and unfairness.
The way governments and institutions have embraced it is atypical and has been pulled off by deluding people that it's actually possible to be "born in the wrong body" or to really somehow "be" the opposite sex and that such people are poor victims and marginalised harmless souls - when it's really not and there is no evidence for that at all. And the bullying and "no debate" tactics and making out that you're a bigot if you have a problem with it. It's been extraordinarily effective, but it's gradually falling apart because reality has a way of persisting and eventually overcoming nonsense.