seems a bit unreasonable to me.
the simple, not specific, answer to when and where the groundswell was would be whenever and wherever there was a bill to ban it.
a bill is a big thing. something that can directly be pointed to, and dated. groundswell by its very definition is the opposite of those things. also very hard to quantify. plenty of the anti-trans bills were DOA, with really only the authors supporting them. would we consider that a start?
as for actual dates, someone pointed to something in 2016 by Obama, which would have predated any type of Trumpian/hate change that drove people to want to push out the trans people first.