no man should be named Ashley

One of my clients was named Tracy. Toughest son of a bitch you'll ever meet..

Ashley has been predominately a male name since it first appeared. For a time, with the spelling changed to Ashleigh, it also served as a female name in Britain.

Ashley as a female name in the US didn't become common until the late 20th century. It is still also used for males, though it has become less common. At the time Margaret Mitchell wrote her book (and at the time of the action) it would have been an almost exclusively a male name.

I would have figured you’d pick on Heathcliff from Wuthering Heights than Ash from GWTW.

*Lots* of names that are *now* overwhelmingly female were overwhelmingly used for boys 100 years ago, e.g.
Alexis
Aubrey
Beverley
Dana
Gale
Hilary
Kim
Lauren
Lindsay
Michele
Reese
Shannon
Shelley
Stacy
Whitney

Other names just used to be gender-neutral but are now feminized, e.g.,
Carol (e.g., O'Connor)
Evelyn (e.g., Waugh)
Marion (e.g., Morrison - John Wayne)
Tracy (e.g., Letts)

And the encroachment continues. According to the Atlantic, in 2017, there were 205 US girls named Ezra at birth, 237 Lincoln, 137 Austin, and 107 Wyatt. They're probably gone as Boys' names by 2040 at the latest.

Interestingly there's little movement/encroachment in the opposite direction either now or in the past. Start your 'What it feels like for a girl' theories:
https://www.youtube.com/watch?v=FrZzbF_sMiQ

https://en.m.wikipedia.org/wiki/Ashley_(name)

https://www.youtube.com/watch?v=CwQHwx-sjlw