I would have tried to get video of the incident. Not easy I'm sure while trying to fly safely and avoid rocks being thrown at your drone. At least you would have proof and possibly a way to identify the women. The way I see it that's no different than throwing rocks at my car while I'm driving. The fact is the made a presumably safe and legal situation and made it dangerous to anyone in close proximity. If they had hit your drone it would have likely going out of control and maybe even struck them. I guess you can't fix stupid.