[pjc50]

In addition to the very good sibling answers: look up what the original Stonewall riot was about. Crossdressing (not the same as being trans! but a necessary precursor) was illegal, and the police could carry out raids and arrest people for wearing gender non-conforming clothing.

This is (just about) in living memory - Donald Trump was 22 years old when the Stonewall riot happened - and there's plenty of people who would like to roll back the law to then. Not just ban trans people but overturn Obergefell v Hodges just like they did with Roe v Wage, end gay marriage, and re-criminalize homosexuality and LGBT expression. Which is why the community rallies against attempts to split off trans people from LGBT.