Look at the issues discussed: gender roles, race/immigration. Conservative means traditional gender roles, immigration as a negative/threat. Liberal means the opposite. For me at least that's comprehensible and unambiguous outside the US as well
I wouldn’t consider anyone who thinks you can only change your gender with surgery a liberal.
This redefines medicine to include literally all human activity, from sartorial preferences to how one crosses their legs. So sure, if we render this term meaningless we can apply it.
Source?
For what it’s worth, I’d call that hard leftist. Not liberal. In the same way I’d call someone insisting on traditional gender labels right wing, not merely conservative. (The latter applying that labelling preference to one’s own children, only.)
And returning to the proximate point, none of that is medicine.